DNV magnetic field detector

ABSTRACT

A system for magnetic detection includes a nitrogen vacancy (NV) diamond material comprising a plurality of NV centers, a radio frequency (RF) excitation source configured to provide RF excitation to the NV diamond material, an optical excitation source configured to provide optical excitation to the NV diamond material, an optical detector configured to receive an optical signal emitted by the NV diamond material, and a controller. The optical signal is based on hyperfine states of the NV diamond material. The controller is configured to detect a gradient of the optical signal based on the hyperfine states emitted by the NV diamond material.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of priority from U.S. ProvisionalPatent Application No. 62/257,988, filed Nov. 20, 2015, which isincorporated herein by reference in its entirety. This applicationclaims priority to U.S. Provisional Application No. 62/190,209, filed onJul. 8, 2015, the entirety of which is incorporated herein by reference.The present application claims priority to U.S. Application No.62/261,643, filed Dec. 1, 2015, which is incorporated by referenceherein in its entirety. The present application claims the benefit ofU.S. Provisional Application Nos. 62/109,006, filed Jan. 28, 2015, and62/109,551, filed Jan. 29, 2015, each of which is incorporated byreference herein in its entirety. The present application claims thebenefit of U.S. Provisional Application No. 62/214,792, filed Sep. 4,2015, which is incorporated by reference herein in its entirety. Thisapplication claims the benefit of priority from U.S. Provisional PatentApplication No. 62/258,003, filed Nov. 20, 2015, which is incorporatedherein by reference in its entirety. This application claims the benefitof priority from U.S. Provisional Patent Application No. 62/190,218,filed Jul. 8, 2015, which is incorporated herein by reference in itsentirety. This application claims the benefit of priority to U.S. PatentApplication No. 62/107,289, filed Jan. 23, 2015, the entire contents ofwhich are incorporated by reference herein in its entirety.

The present application is related to co-pending U.S. application Ser.No. 15/003,558, filed Jan. 21, 2016, titled “APPARATUS AND METHOD FORHYPERSENSITIVITY DETECTION OF MAGNETIC FIELD,” which is incorporated byreference herein in its entirety. The present application is related toco-pending U.S. application Ser. No. 15/003,062, filed Jan. 21, 2016,titled “IMPROVED LIGHT COLLECTION FROM DNV SENSORS,” which isincorporated by reference herein in its entirety. The presentapplication is related to co-pending U.S. application Ser. No.15/003,652, filed Jan. 21, 2016, titled “PRECISION POSITIONENCODER/SENSOR USING NITROGEN VACANCY DIAMOND,” which is incorporated byreference herein in its entirety. The present application is related toco-pending U.S. application Ser. No. 15/003,677, filed Jan. 21, 2016,titled “COMMUNICATION VIA A MAGNIO,” which is incorporated by referenceherein in its entirety. The present application is related to co-pendingU.S. application Ser. No. 15/003,678, filed Jan. 21, 2016, titled“METHOD FOR RESOLVING NATURAL SENSOR AMBIGUITY FOR DNV DIRECTION FINDINGAPPLICATIONS,” which is incorporated by reference herein in itsentirety. The present application is related to co-pending U.S.application Ser. No. 15/003,177, filed Jan. 21, 2016, titled“HYDROPHONE,” which is incorporated by reference herein in its entirety.The present application is related to co-pending U.S. application Ser.No. 15/003,206, filed Jan. 21, 2016, titled “MAGNETIC NAVIGATION METHODSAND SYSTEMS UTILIZING POWER GRID AND COMMUNICATION NETWORK,” which isincorporated by reference herein in its entirety. The presentapplication is related to co-pending U.S. application Ser. No.15/003,193, filed Jan. 21, 2016, titled “RAPID HIGH-RESOLUTION MAGNETICFIELD MEASUREMENTS FOR POWER LINE INSPECTION,” which is incorporated byreference herein in its entirety. The present application is related toco-pending U.S. application Ser. No. 15/003,088, filed Jan. 21, 2016,titled “IN-SITU POWER CHARGING,” which is incorporated by referenceherein in its entirety. The present application is related to co-pendingU.S. patent application Ser. No. 15/003,519, filed Jan. 21, 2016, titled“APPARATUS AND METHOD FOR CLOSED LOOP PROCESSING FOR A MAGNETICDETECTION SYSTEM,” which is incorporated by reference herein in itsentirety. The present application is related to co-pending U.S.application Ser. No. 15/003,718, filed Jan. 21, 2016, titled “APPARATUSAND METHOD FOR RECOVERY OF THREE DIMENSIONAL MAGNETIC FIELD FROM AMAGNETIC DETECTION SYSTEM,” which is incorporated by reference herein inits entirety. The present application is related to co-pending U.S.application Ser. No. 15/003,209, filed Jan. 21, 2016, titled “DIAMONDNITROGEN VACANCY SENSED FERRO-FLUID HYDROPHONE,” which is incorporatedby reference herein in its entirety. The present application is relatedto co-pending U.S. application Ser. No. 15/003,670, filed Jan. 21, 2016,titled “AC VECTOR MAGNETIC ANOMALY DETECTION WITH DIAMOND NITROGENVACANCIES,” which is incorporated by reference herein in its entirety.The present application is related to co-pending U.S. application Ser.No. 15/003,704, filed Jan. 21, 2016, titled “APPARATUS AND METHOD FORESTIMATING ABSOLUTE AXES' ORIENTATIONS FOR A MAGNETIC DETECTION SYSTEM,”which is incorporated by reference herein in its entirety. The presentapplication is related to co-pending U.S. application Ser. No.15/003,590, filed Jan. 21, 2016, titled “APPARATUS AND METHOD FOR HIGHSENSITIVITY MAGNETOMETRY MEASUREMENT AND SIGNAL PROCESSING IN A MAGNETICDETECTION SYSTEM,” which is incorporated by reference herein in itsentirety. The present application is related to co-pending U.S.application Ser. No. 15/003,176, filed Jan. 21, 2016, titled “MAGNETICBAND-PASS FILTER,” which is incorporated by reference herein in itsentirety. The present application is related to co-pending U.S.application Ser. No. 15/003,145, filed Jan. 21, 2016, titled “DEFECTDETECTOR FOR CONDUCTIVE MATERIALS,” which is incorporated by referenceherein in its entirety. The present application is related to co-pendingU.S. application Ser. No. 15/003,309, filed Jan. 21, 2016, titled“DIAMOND NITROGEN VACANCY SENSOR WITH DUAL RF SOURCES,” which isincorporated by reference herein in its entirety. The presentapplication is related to co-pending U.S. application Ser. No.15/003,298, filed Jan. 21, 2016, titled “DIAMOND NITROGEN VACANCY SENSORWITH COMMON RF AND MAGNETIC FIELDS GENERATOR,” which is incorporated byreference herein in its entirety. The present application is related toco-pending U.S. application Ser. No. 15/003,292, filed Jan. 21, 2016,titled “MAGNETOMETER WITH A LIGHT EMITTING DIODE,” which is incorporatedby reference herein in its entirety. The present application is relatedto co-pending U.S. application Ser. No. 15/003,281, filed Jan. 21, 2016,titled “MAGNETOMETER WITH LIGHT PIPE,” which is incorporated byreference herein in its entirety. The present application is related toco-pending U.S. application Ser. No. 15/003,634, filed Jan. 21, 2016,titled “DIAMOND NITROGEN VACANCY SENSOR WITH CIRCUITRY ON DIAMOND,”which is incorporated by reference herein in its entirety. The presentapplication is related to co-pending U.S. application Ser. No.15/003,577, filed Jan. 21, 2016, titled “MEASUREMENT PARAMETERS FOR QCMETROLOGY OF SYNTHETICALLY GENERATED DIAMOND WITH NV CENTERS,” which isincorporated by reference herein in its entirety. The presentapplication is related to co-pending U.S. application Ser. No.15/003,256, filed Jan. 21, 2016, titled “HIGHER MAGNETIC SENSITIVITYTHROUGH FLUORESCENCE MANIPULATION BY PHONON SPECTRUM CONTROL,” which isincorporated by reference herein in its entirety. The presentapplication is related to co-pending U.S. application Ser. No.15/003,396, filed Jan. 21, 2016, titled “MAGNETIC WAKE DETECTOR,” whichis incorporated by reference herein in its entirety. The presentapplication is related to co-pending U.S. application Ser. No.15/003,617, filed Jan. 21, 2016, titled “GENERAL PURPOSE REMOVAL OFGEOMAGNETIC NOISE,” which is incorporated by reference herein in itsentirety. The present application is related to co-pending U.S.application Ser. No. 15/003,336, filed Jan. 21, 2016, titled “REDUCEDINSTRUCTION SET CONTROLLER FOR DIAMOND NITROGEN VACANCY SENSOR,” whichis incorporated by reference herein in its entirety. The presentapplication is related to co-pending U.S. application Ser. No.14/676,740, filed Apr. 1, 2015, titled “HIGH BIT-RATE MAGNETICCOMMUNICATION,” which is incorporated by reference herein in itsentirety.

FIELD

The present disclosure generally relates to magnetometers.

BACKGROUND

Atomic-sized nitrogen-vacancy (NV) centers in diamond lattices have beenshown to have excellent sensitivity for magnetic field measurement andenable fabrication of small magnetic sensors that can readily replaceexisting-technology (e.g., Hall-effect, SERF, SQUID, or the like)systems and devices. Nitrogen vacancy diamond (DNV) magnetometers areable to sense extremely small magnetic field variations by changes inthe diamond's red photoluminescence that relate, through the gradient ofthe luminescent function, to frequency and thereafter to magnetic fieldthrough the Zeeman effect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one orientation of an NV center in a diamond lattice.

FIG. 2 is an energy level diagram showing energy levels of spin statesfor the NV center.

FIG. 3 is a schematic illustrating an NV center magnetic sensor system.

FIG. 4 is a graph illustrating a fluorescence as a function of anapplied RF frequency of an NV center along a given direction for a zeromagnetic field.

FIG. 5 is a graph illustrating the fluorescence as a function of anapplied RF frequency for four different NV center orientations for anon-zero magnetic field.

FIG. 6 is a schematic diagram illustrating a magnetic field detectionsystem according to an embodiment of the present invention.

FIG. 7 is a graph illustrating a fluorescence as a function of anapplied RF frequency for an NV center orientation in a non-zero magneticfield and a gradient of the fluorescence as a function of the applied RFfrequency.

FIG. 8 is an energy level diagram showing a hyperfine structure of spinstates for the NV center.

FIG. 9 is a graph illustrating a fluorescence as a function of anapplied RF frequency for an NV center orientation in a non-zero magneticfield with hyperfine detection and a gradient of the fluorescence as afunction of the applied RF frequency.

FIG. 10 is an overview of a reflector with a diamond having nitrogenvacancies.

FIG. 11 is a side view of an ellipsoidal reflector with a diamond havingnitrogen vacancies and a photo detector.

FIG. 12 is a side view of an ellipsoidal diamond having nitrogenvacancies and a photo detector.

FIG. 13 is a side view of a parabolic reflector with a diamond havingnitrogen vacancies and a photo detector.

FIG. 14 is a side view of a parabolic diamond having nitrogen vacanciesand a photo detector.

FIG. 15 is a side view of a parabolic reflector with a flat diamondhaving nitrogen vacancies inserted parallel to a major axis of theparabolic reflector and a photo detector.

FIG. 16 is a side view of a parabolic reflector with a flat diamondhaving nitrogen vacancies inserted parallel to a minor axis of theparabolic reflector and a photo detector.

FIG. 17 is a side view of a sensor assembly with a parabolic diamondhaving nitrogen vacancies and a photo detector.

FIG. 18 is a side view of a sensor assembly with a waveguide providedwithin a parabolic reflector.

FIG. 19 is a process diagram for a method for constructing a DNV sensor.

FIG. 20 is another process diagram for a method for constructing a DNVsensor.

FIG. 21 is a block diagram depicting a general architecture for acomputer system that may be employed to implement various elements ofthe systems and methods described and illustrated herein.

FIG. 22 is a schematic illustrating a position sensor system accordingto one embodiment.

FIG. 23 is a schematic illustrating a position sensor system including arotary position encoder.

FIG. 24 is a schematic illustrating a top down view of a rotary positionencoder.

FIG. 25 is a schematic illustrating a position sensor system including alinear position encoder.

FIG. 26 is a schematic illustrating a magnetic element arrangement of aposition encoder according to one embodiment.

FIG. 27 is a schematic illustrating a magnetic element arrangement of aposition encoder according to another embodiment.

FIG. 28 is a schematic illustrating a magnetic element arrangement of aposition encoder according to another embodiment.

FIG. 29 is a schematic illustrating the relationship of a positionsensor head and the magnetic elements of a position encoder.

FIG. 30 is a graph of measured magnetic field intensity attributable tomagnetic elements of a position encoder for a first magnetic fieldsensor and a second magnetic field sensor of a position sensor head.

FIG. 31 is a flow chart illustrating the process of determining aposition utilizing a position sensor system according to one embodiment.

FIGS. 32A and 32B are graphs illustrating the frequency response of aDNV sensor in accordance with an illustrative embodiment.

FIG. 33A is a diagram of NV center spin states in accordance with anillustrative embodiment.

FIG. 33B is a graph illustrating the frequency response of a DNV sensorin response to a changed magnetic field in accordance with anillustrative embodiment.

FIG. 34 is a block diagram of a magnetic communication system inaccordance with an illustrative embodiment.

FIGS. 35A and 35B show the strength of a magnetic field versus frequencyin accordance with an illustrative embodiment.

FIG. 36 is a block diagram of a computing device in accordance with anillustrative embodiment.

FIG. 37 is graphs illustrating the fluorescence as a function of appliedRF frequency of four different NV center orientations for a magneticfield applied in opposite directions to the NV center diamond material.

FIG. 38 is a graph illustrating the fluorescence intensity as a functionof time for a NV center diamond material with a pulsed RF excitation.

FIG. 39 is a graph illustrating the fluorescence as a function ofapplied RF frequency of four different NV center orientations for amagnetic field applied in opposite directions to the NV center diamondmaterial, with a Lorentzian pair being identified in the graph.

FIG. 40 is a graph illustrating the fluorescence intensity as a functionof time for a NV center diamond material for a pulse of RF excitation.

FIG. 41 is a graph illustrating the normalized fluorescence intensity asa function of time for a pair of Lorentzian peaks of a NV center diamondmaterial.

FIG. 42 is a graph illustrating the time to 60% of the equilibriumfluorescence as a function of RF frequency for a negative and positivemagnetic bias field applied to a NV center diamond material.

FIGS. 43A and 43B are diagrams illustrating hydrophone systems inaccordance with illustrative embodiments.

FIG. 44 illustrates a low altitude flying object in accordance with someillustrative implementations.

FIG. 45A illustrates a ratio of signal strength of two magnetic sensors,A and B, attached to wings of the UAS as a function of distance, x, froma center line of a power in accordance with some illustrativeimplementations.

FIG. 45B illustrates a composite magnetic field (B-filed) in accordancewith some illustrative implementations.

FIG. 46 illustrates a high-level block diagram of an example UASnavigation system in accordance with some illustrative implementations.

FIG. 47 illustrates an example of a power line infrastructure.

FIGS. 48A and 48B illustrate examples of magnetic field distribution foroverhead power lines and underground power cables.

FIG. 49 illustrates examples of magnetic field strength of power linesas a function of distance from the centerline.

FIG. 50 illustrates an example of a UAS equipped with DNV sensors inaccordance with some illustrative implementations.

FIG. 51 illustrates a plot of a measured differential magnetic fieldsensed by the DNV sensors when in close proximity of the power lines inaccordance with some illustrative implementations.

FIG. 52 illustrates an example of a measured magnetic field distributionfor normal power lines and power lines with anomalies according to someimplementations.

DETAILED DESCRIPTION

Hypersensitivity Detection of Magnetic Field

Aspects of the disclosure relates to apparatuses and methods forelucidating hyperfine transition responses to determine an externalmagnetic field acting on a magnetic detection system. The hyperfinetransition responses exhibit a steeper gradient than the gradient ofaggregate Lorentzian responses measured in conventional systems, whichcan be up to three orders of magnitude larger. The steeper gradientexhibited by the hyperfine transition responses thus allow for acomparable increase in measurement sensitivity in a magnetic detectionsystem. By utilizing the largest gradient of the hyperfine responses formeasuring purposes, external magnetic fields may be detected moreaccurately, especially low magnitude and/or rapidly changing fields.

The NV Center, its Electronic Structure, and Optical and RF Interaction

The NV center in a diamond comprises a substitutional nitrogen atom in alattice site adjacent a carbon vacancy as shown in FIG. 1. The NV centermay have four orientations, each corresponding to a differentcrystallographic orientation of the diamond lattice.

The NV center may exist in a neutral charge state or a negative chargestate. Conventionally, the neutral charge state uses the nomenclatureNV⁰, while the negative charge state uses the nomenclature NV, which isadopted in this description.

The NV center has a number of electrons, including three unpairedelectrons, each one from the vacancy to a respective of the three carbonatoms adjacent to the vacancy, and a pair of electrons between thenitrogen and the vacancy. The NV center, which is in the negativelycharged state, also includes an extra electron.

The NV center has rotational symmetry, and as shown in FIG. 2, has aground state, which is a spin triplet with ³A₂ symmetry with one spinstate m_(s)=0, and two further spin states m_(s)=+1, and m_(s)=−1. Inthe absence of an external magnetic field, the m_(s)=±1 energy levelsare offset from the m_(s)=0 due to spin-spin interactions, and them_(s)=±1 energy levels are degenerate, i.e., they have the same energy.The m_(s)=0 spin state energy level is split from the m_(s)=±1 energylevels by an energy of 2.87 GHz for a zero external magnetic field.

Introducing an external magnetic field with a component along the NVaxis lifts the degeneracy of the m_(s)=±1 energy levels, splitting theenergy levels m_(s)=±1 by an amount 2gμ_(B)Bz, where g is the g-factor,μ_(B) is the Bohr magneton, and Bz is the component of the externalmagnetic field along the NV axis. This relationship is correct to afirst order and inclusion of higher order corrections is straightforwardmatter and will not affect the computational and logic steps in thesystems and methods described below.

The NV center electronic structure further includes an excited tripletstate ³E with corresponding m_(s)=0 and m_(s)=±1 spin states. Theoptical transitions between the ground state ³A₂ and the excited triplet³E are predominantly spin conserving, meaning that the opticaltransitions are between initial and final states that have the samespin. For a direct transition between the excited triplet ³E and theground state ³A₂, a photon of red light is emitted with a photon energycorresponding to the energy difference between the energy levels of thetransitions.

There is, however, an alternative non-radiative decay route from thetriplet ³E to the ground state ³A₂ via intermediate electron states,which are thought to be intermediate singlet states A, E withintermediate energy levels. Significantly, the transition rate from them_(s)=±1 spin states of the excited triplet ³E to the intermediateenergy levels is significantly greater than the transition rate from them_(s)=0 spin state of the excited triplet ³E to the intermediate energylevels. The transition from the singlet states A, E to the ground statetriplet ³A₂ predominantly decays to the m_(s)=0 spin state over them_(s)=−1 spins states. These features of the decay from the excitedtriplet ³E state via the intermediate singlet states A, E to the groundstate triplet ³A₂ allows that if optical excitation is provided to thesystem, the optical excitation will eventually pump the NV center intothe m_(s)=0 spin state of the ground state ³A₂. In this way, thepopulation of the m_(s)=0 spin state of the ground state ³A₂ may be“reset” to a maximum polarization determined by the decay rates from thetriplet ³E to the intermediate singlet states.

Another feature of the decay is that the fluorescence intensity due tooptically stimulating the excited triplet ³E state is less for them_(s)=±1 states than for the m_(s)=0 spin state. This is so because thedecay via the intermediate states does not result in a photon emitted inthe fluorescence band, and because of the greater probability that them_(s)=±1 states of the excited triplet ³E state will decay via thenon-radiative decay path. The lower fluorescence intensity for them_(s)=±1 states than for the m_(s)=0 spin state allows the fluorescenceintensity to be used to determine the spin state. As the population ofthe m_(s)=±1 states increases relative to the m_(s)=0 spin, the overallfluorescence intensity will be reduced.

The NV Center, or Magneto-Optical Defect Center, Magnetic Sensor System

FIG. 3 is a schematic diagram illustrating a conventional NV centermagnetic sensor system 300 that uses fluorescence intensity todistinguish the m_(s)=±1 states, and to measure the magnetic field basedon the energy difference between the m_(s)=+1 state and the m_(s)=−1state. The system 300 includes an optical excitation source 310, whichdirects optical excitation to an NV diamond material 320 with NVcenters. The system further includes an RF excitation source 330, whichprovides RF radiation to the NV diamond material 320. Light from the NVdiamond may be directed through an optical filter 350 to an opticaldetector 340.

The RF excitation source 330 may be a microwave coil, for example. TheRF excitation source 330, when emitting RF radiation with a photonenergy resonant with the transition energy between ground m_(s)=0 spinstate and the m_(s)=+1 spin state, excites a transition between thosespin states. For such a resonance, the spin state cycles between groundm_(s)=0 spin state and the m_(s)=+1 spin state, reducing the populationin the m_(s)=0 spin state and reducing the overall fluorescence atresonances. Similarly, resonance occurs between the m_(s)=0 spin stateand the m_(s)=−1 spin state of the ground state when the photon energyof the RF radiation emitted by the RF excitation source is thedifference in energies of the m_(s)=0 spin state and the m_(s)=−1 spinstate, or between the m_(s)=0 spin state and the m_(s)=+1 spin state,there is a decrease in the fluorescence intensity.

The optical excitation source 310 may be a laser or a light emittingdiode, for example, which emits light in the green, for example. Theoptical excitation source 310 induces fluorescence in the red, whichcorresponds to an electronic transition from the excited state to theground state. Light from the NV diamond material 320 is directed throughthe optical filter 350 to filter out light in the excitation band (inthe green, for example), and to pass light in the red fluorescence band,which in turn is detected by the detector 340. The optical excitationlight source 310, in addition to exciting fluorescence in the diamondmaterial 320, also serves to reset the population of the m_(s)=0 spinstate of the ground state ³A₂ to a maximum polarization, or otherdesired polarization.

For continuous wave excitation, the optical excitation source 310continuously pumps the NV centers, and the RF excitation source 330sweeps across a frequency range that includes the zero splitting (whenthe m_(s)=±1 spin states have the same energy) energy of 2.87 GHz. Thefluorescence for an RF sweep corresponding to a diamond material 320with NV centers aligned along a single direction is shown in FIG. 4 fordifferent magnetic field components Bz along the NV axis, where theenergy splitting between the m_(s)=−1 spin state and the m_(s)=+1 spinstate increases with Bz. Thus, the component Bz may be determined.Optical excitation schemes other than continuous wave excitation arecontemplated, such as excitation schemes involving pulsed opticalexcitation, and pulsed RF excitation. Examples of pulsed excitationschemes include Ramsey pulse sequence, and spin echo pulse sequence.

In general, the diamond material 320 will have NV centers aligned alongdirections of four different orientation classes. FIG. 5 illustratesfluorescence as a function of RF frequency for the case where thediamond material 320 has NV centers aligned along directions of fourdifferent orientation classes. In this case, the component Bz along eachof the different orientations may be determined. These results, alongwith the known orientation of crystallographic planes of a diamondlattice, allow not only the magnitude of the external magnetic field tobe determined, but also the direction of the magnetic field.

While FIG. 3 illustrates an NV center magnetic sensor system 300 with NVdiamond material 320 with a plurality of NV centers, in general, themagnetic sensor system may instead employ a different magneto-opticaldefect center material, with a plurality of magneto-optical defectcenters. The electronic spin state energies of the magneto-opticaldefect centers shift with magnetic field, and the optical response, suchas fluorescence, for the different spin states is not the same for allof the different spin states. In this way, the magnetic field may bedetermined based on optical excitation, and possibly RF excitation, in acorresponding way to that described above with NV diamond material.

FIG. 6 is a schematic diagram of a system 600 for a magnetic fielddetection system according to an embodiment of the present invention.The system 600 includes an optical excitation source 610, which directsoptical excitation to an NV diamond material 620 with NV centers, oranother magneto-optical defect center material with magneto-opticaldefect centers. An RF excitation source 630 provides RF radiation to theNV diamond material 620.

As shown in FIG. 6, a first magnetic field generator 670 generates amagnetic field, which is detected at the NV diamond material 620. Thefirst magnetic field generator 670 may be a permanent magnet positionedrelative to the NV diamond material 620, which generates a known,uniform magnetic field (e.g., a bias or control magnetic field) toproduce a desired fluorescence intensity response from the NV diamondmaterial 620. In some embodiments, a second magnetic field generator 675may be provided and positioned relative to the NV diamond material 620to provide an additional bias or control magnetic field. The secondmagnetic field generator 675 may be configured to generate magneticfields with orthogonal polarizations, for example. In this regard, thesecond magnetic field generator 675 may include one or more coils, suchas a Helmholtz coils. The coils may be configured to provide relativelyuniform magnetic fields at the NV diamond material 620 and each maygenerate a magnetic field having a direction that is orthogonal to thedirection of the magnetic field generated by the other coils. Forexample, in a particular embodiment, the second magnetic field generator675 may include three Helmholtz coils that are arranged to each generatea magnetic field having a direction orthogonal to the other direction ofthe magnetic field generated by the other two coils resulting in athree-axis magnetic field. In some embodiments, only the first magneticfield generator 670 may be provided to generate a bias or controlmagnetic field. Alternatively, only the second magnetic field generator675 may be provided to generate the bias or control magnetic field. Inyet other embodiments, the first and/or second magnetic field generatorsmay be affixed to a pivot assembly (e.g., a gimbal assembly) that may becontrolled to hold and position the first and/or second magnetic fieldgenerators to a predetermined and well-controlled set of orientations,thereby establishing the desired bias or control magnetic fields. Inthis case, the controller 680 may be configured to control the pivotassembly having the first and/or second magnetic field generators toposition and hold the first and/or second magnetic field generators atthe predetermined orientation.

The system 600 further includes a controller 680 arranged to receive alight detection or optical signal from the optical detector 640 and tocontrol the optical excitation source 610, the RF excitation source 630,and the second magnetic field generator 675. The controller may be asingle controller, or multiple controllers. For a controller includingmultiple controllers, each of the controllers may perform differentfunctions, such as controlling different components of the system 600.The second magnetic field generator 675 may be controlled by thecontroller 680 via an amplifier 660, for example.

The RF excitation source 630 may be a microwave coil, for example. TheRF excitation source 630 is controlled to emit RF radiation with aphoton energy resonant with the transition energy between the groundm_(s)=0 spin state and the m_(s)=±1 spin states as discussed above withrespect to FIG. 3.

The optical excitation source 610 may be a laser or a light emittingdiode, for example, which emits light in the green, for example. Theoptical excitation source 610 induces fluorescence in the red from theNV diamond material 620, where the fluorescence corresponds to anelectronic transition from the excited state to the ground state. Lightfrom the NV diamond material 620 is directed through the optical filter650 to filter out light in the excitation band (in the green, forexample), and to pass light in the red fluorescence band, which in turnis detected by the optical detector 640. The optical excitation lightsource 610, in addition to exciting fluorescence in the NV diamondmaterial 620, also serves to reset the population of the m_(s)=0 spinstate of the ground state ³A₂ to a maximum polarization, or otherdesired polarization.

The controller 680 is arranged to receive a light detection signal fromthe optical detector 640 and to control the optical excitation source610, the RF excitation source 630, and the second magnetic fieldgenerator 675. The controller may include a processor 682 and a memory684, in order to control the operation of the optical excitation source610, the RF excitation source 630, and the second magnetic fieldgenerator 675. The memory 684, which may include a nontransitorycomputer readable medium, may store instructions to allow the operationof the optical excitation source 610, the RF excitation source 630, andthe second magnetic field generator 675 to be controlled. That is, thecontroller 680 may be programmed to provide control.

Detection of Magnetic Field Changes

As discussed above, the interaction of the NV centers with an externalmagnetic field results in an energy splitting between the m_(s)=−1 spinstate and the m_(s)=+1 spin state that increases with Bz as shown inFIG. 4, for example. The pair of frequency responses (also known asLorentzian responses, profiles, or dips) due to the component of theexternal magnetic field along the given NV axis manifest as dips inintensity of the emitted red light from the NV centers as a function ofRF carrier frequency. Accordingly, a pair of frequency responses foreach of the four axes of the NV center diamond lattice result in anenergy splitting between the m_(s)=−1 spin state and the m_(s)=+1 spinstate that corresponds to the component of the external magnetic fieldalong the axis for a total of eight Lorentzian profiles or dips, asshown in FIG. 5. When a bias magnetic field is applied to the NV diamondmaterial (such as by the first and/or second magnetic field generators670, 675 of FIG. 6), in addition to an unknown external magnetic fieldexisting outside the system, the total incident magnetic field may thusbe expressed as B_(t)(t)=B_(bias)(t)+B_(ext)(t), where B_(bias)(t)represents the bias magnetic field applied to the NV diamond materialand B_(ext)(t) represents the unknown external magnetic field. Thistotal incident magnetic field creates equal and linearly proportionalshifts in the Lorentzian frequency profiles for a given NV axis betweenthe m_(s)=−1 spin state and the m_(s)=+1 spin state relative to thestarting carrier frequency (e.g., about 2.87 GHz).

Because the applied bias magnetic field B_(bias)(t) is already known andconstant, a change or shift in the total incident magnetic fieldB_(t)(t) will be due to a change in the external magnetic fieldB_(ext)(t). To detect a change in the total incident magnetic field, thepoint of greatest sensitivity in measuring such a change will occur atthe point where the frequency response is at its largest slope. Forexample, as shown in FIG. 7, an intensity response I(t) as a function ofan RF applied frequency f(t) for a given NV axis due to a magnetic fieldis shown in the top graph. The change in intensity I(t) relative to thechange in RF applied frequency,

$\frac{d\;{I(t)}}{d\; f},$is plotted against the RF applied frequency f(t) as shown in the bottomgraph. Point 25 represents the point of the greatest gradient of theLorentzian dip 20. This point gives the greatest measurement sensitivityin detecting changes in the total incident magnetic field as it respondsto the external magnetic field.

The Hyperfine Field

As discussed above and shown in the energy level diagram of FIG. 2, theground state is split by about 2.87 GHz between the m_(s)=0 and m_(s)=±1spin states due to their spin-spin interactions. In addition, due to thepresence of a magnetic field, the m_(s)=±1 spin states split inproportion to the magnetic field along the given axis of the NV center,which manifests as the four-pair Lorentzian frequency response shown inFIG. 5. However, a hyperfine structure of the NV center exists due tothe hyperfine coupling between the electronic spin states of the NVcenter and the nitrogen nucleus, which results in further energysplitting of the spin states. FIG. 8 shows the hyperfine structure ofthe ground state triplet ³A₂ of the NV center. Specifically, coupling tothe nitrogen nucleus ¹⁴N further splits the m_(s)=±1 spin states intothree hyperfine transitions (labeled as m_(I) spin states), each havingdifferent resonances. Accordingly, due to the hyperfine split for eachof the m_(s)=±1 spin states, twenty-four different frequency responsesmay be produced (three level splits for each of the m_(s)=±1 spin statesfor each of the four NV center orientations).

Each of the three hyperfine transitions manifest within the width of oneaggregate Lorentzian dip. With proper detection, the hyperfinetransitions may be elucidated within a given Lorentzian response. Todetect such hyperfine transitions, in particular embodiments, the NVdiamond material 620 exhibits a high purity (e.g., low existence oflattice dislocations, broken bonds, or other elements beyond ¹⁴N) anddoes not have an excess concentration of NV centers. In addition, duringoperation of the system 600 in some embodiments, the RF excitationsource 630 is operated on a low power setting in order to furtherresolve the hyperfine responses. In other embodiments, additionaloptical contrast for the hyperfine responses may be accomplished byincreasing the concentration of NV negative-charge type centers,increasing the optical power density (e.g., in a range from about 20 toabout 1000 mW/mm²), and decreasing the RF power to the lowest magnitudethat permits a sufficient hyperfine readout (e.g., about 1 to about 10W/mm²).

FIG. 9 shows an example of fluorescence intensity as a function of anapplied RF frequency for an NV center with hyperfine detection. In thetop graph, the intensity response I(t) as a function of an applied RFfrequency f(t) for a given spin state (e.g., m_(s)=−1) along a givenaxis of the NV center due to an external magnetic field is shown. Inaddition, in the bottom graph, the gradient

$\frac{{dI}(t)}{df}$plotted against the applied RF frequency f(t) is shown. As seen in thefigure, the three hyperfine transitions 900 a-900 c constitute acomplete Lorentzian response 20 (e.g., corresponding to the Lorentzianresponse 20 in FIG. 7). The point of maximum slope may then bedetermined through the gradient of the fluorescence intensity as afunction of the applied RF frequency, which occurs at the point 950 inFIG. 9. This point of maximum slope may then be tracked during theapplied RF sweep to detect movement of the point of maximum slope alongthe frequency sweep. Like the point of maximum slope 25 for theaggregate Lorentzian response, the corresponding movement of the point950 corresponds to changes in the total incident magnetic fieldB_(t)(t), which because of the known and constant bias fieldB_(bias)(t), allows for the detection of changes in the externalmagnetic field B_(ext)(t).

However, as compared to point 25, point 950 exhibits a larger gradientthan the aggregate Lorentzian gradient described above with regard toFIG. 7. In some embodiments, the gradient of point 950 may be up to 1000times larger than the aggregate Lorentzian gradient of point 25. Due tothis, the point 950 and its corresponding movement may be more easilydetected by the measurement system resulting in improved sensitivity,especially in very low magnitude and/or very rapidly changing magneticfields.

Improved Light Collection from DNV Sensors

In some aspects of the present technology, methods and configurationsare disclosed for an efficient collection of fluorescence (e.g., redlight) emitted by the nitrogen vacancies of a diamond of a DNV sensor.In some implementations, the subject technology can allow efficientcollection of the emitted light of the diamond of the DNV sensor with acompact and low cost reflector. The reflector can focus the emittedlight of the diamond of the DNV sensor to an optical or photo detectorthat can increase the amount of light detected from the diamond. In someimplementations, such a configuration may detect virtually all lightemitted by the diamond of the DNV sensor. In some aspects, the reflectormay be shaped as a parabola, an ellipse, or other shapes that can conveythe light emitted from a source to a focal point or focal area.

In some other implementations of the subject technology, the diamond ofthe DNV sensor may be machined or otherwise shaped to be a reflectoritself. That is, the diamond with nitrogen vacancies may be shaped toform a parabolic reflector, ellipsoidal reflector or other shapes thatcan convey the light emitted from the nitrogen vacancies to a focalpoint or focal area. For example, the reflector can be mostly parabolicor ellipsoidal such that the light hits the photo detector at a 90degree angle with some margin of error, e.g., 2 to 10 degrees.

The nitrogen vacancies of the diamond will fluoresce in response toexcitation with green light and will emit red light in randomdirections. Because the red light measurements are shot noise limited,collecting as much emitted light as possible is desirable. In somecurrent collection approaches using large optics, the collectionefficiencies were in the range of 20%. Some implementations use a largeaperture lens mounted close to the diamond or DNV sensor, which limitslight collection to a fraction of the light emitted by the diamond orDNV sensor. Other implementations use a flat diamond and a number ofphoto detectors (e.g., four) positioned at the edges of the flatdiamond. This arrangement of photo detectors may be able to capture moreof the emitted light conducted to edges of the flat diamond due tointernal reflection, but increases the number of photo detectorsrequired and may not capture light emitted from the faces of the flatdiamond. The DNV sensors discussed herein provide an alternative toincrease the collection efficiency.

FIG. 10 depicts an overview of an assembly 1000 with an example diamond1002 having nitrogen vacancies and a reflector 1004 positioned about thediamond 1002 for a DNV light-collection apparatus. In the implementationshown, the reflector 1004 is positioned about the diamond 1002 toreflect a portion of the light emitted 1006 from the diamond 1002. Thereflector 1004 is an elliptical or ellipsoidal reflector with thediamond 1002 positioned within a portion of the reflector 1004. In otherimplementations, as discussed in further detail herein, the reflector1004 may be parabolic or any other geometric configuration to reflectlight emitted from the diamond 1002. In some implementations, thereflector 1004 may be a monolithic reflector, a hollow reflector, or anyother type of reflector to reflect light emitted from the diamond 1002.In the implementation shown, the diamond 1002 is positioned at a focus1008 of the reflector 1004. Thus, when light 1006 is emitted from thediamond 1002, the light is reflected by the reflector 1004 towardanother focus of the reflector 1004. As will be discussed in furtherdetail herein, a photo detector may be positioned at the second focus tocollect the reflected light.

FIG. 11 depicts an assembly 1100 with an example diamond 1102 havingnitrogen vacancies and an ellipsoidal reflector 1104 positioned aboutthe diamond 1102 for a DNV light-collection apparatus. In someimplementations, the ellipsoidal reflector 1104 can be a singlemonolithic component that can be considered to be divided into twoportions, such as a reflector portion 1106 and a concentrator portion1108. In other implementations, the ellipsoidal reflector 1104 may bedivided into two components, such as the reflector portion 1106 and theconcentrator portion 1108 that are coupled and/or otherwise positionedrelative to each other. For instance, the reflector portion 1106 and theconcentrator portion 1108 may be separate parabolic components that canbe combined to form the ellipsoidal reflector 1104. In still furtherconfigurations, the ellipsoidal reflector 1104 may be composed of morethan two components and can be coupled or otherwise positioned to formthe ellipsoidal reflector 1104.

The diamond 1102 is positioned at a first focus of the ellipsoidalreflector 1104 for the reflector portion 1106. In some implementations,the diamond 1102 is positioned at the first focus using a mount for thediamond 1102. In other implementations, the diamond 1102 is positionedat the first focus using a borehole through the ellipsoidal reflector1104. The borehole may be backfilled to seal the diamond 1102 in theellipsoidal reflector 1104.

The ellipsoidal reflector 1104 may also include an opening to allow anexcitation laser beam to excite the diamond 1102, such as a greenexcitation laser beam. The opening may be positioned at any location forthe ellipsoidal reflector 1104. When the diamond 1102 is excited (e.g.,by applying green light to the diamond 1102), then the reflector portion1106 reflects the red light emitted 1110 from the diamond 1102 towardsthe concentrator portion 1108.

The concentrator portion 1108 directs the emitted light 1110 toward asecond focus of the ellipsoidal reflector 1104. In the implementationshown, a photo detector 1120 is positioned to receive and measure thelight from the concentrator portion 1108. In some implementations, thephoto detector 1120 is positioned at the second focus to receive theredirected emitted light. In some implementations the photo detector1120 is coupled and/or sealed to a portion of the ellipsoidal reflector1104, such as to the concentrator portion 1108. In some implementations,the opening may be adjacent or proximate to the photo detector 1120,such as through the concentrator portion 1108. In other implementations,the opening may be opposite the photo detector 1120, such as through thereflector portion 1106. In still further configurations, the opening maybe at any other angle and/or orientation relative to the photo detector1120.

In some implementations, an optical filter, such as a red filter, may beapplied to and/or positioned on the photo detector 1120 to filter outlight except the relevant red light of interest. Thus, the ellipsoidalreflector 1104 is concatenated with a non-focusing concentrator that cancapture the emitted light from a light source (e.g., from the nitrogenvacancies of the diamond of a DNV sensor) to a single photo detector. Insome instances, the loss of emitted light can be limited to the lightloss due to the mount for the diamond and/or the small entrance for thegreen stimulation laser beam.

The foregoing solution provides high light collection efficiency tocollect the light emitted from the diamond 1102, while utilizing areflector 1104 that may not require high precision refinements. Such areflector 1104 may be a low cost solution to increase the lightcollection efficiency, such as using a reflective mirror component. Inaddition, the shape of the ellipsoidal reflector 1104 may separate theelectronics of the photo detector 1120 from the diamond 1102, which maydecrease the magnetic interaction between the electronics of the photodetector 1120 and the diamond 1102.

The elliptical reflector 1104 may, in some implementations, include asubstrate with a dielectric mirror film or coating applied to reflectthe emitted light 1110. The dielectric mirror film may be selected forthe specific frequency of interest. In some implementations, thethickness of the dielectric mirror material may affect the specificfrequency of interest. For instance, the substrate may possess a highclarity at a frequency of interest for the DNV sensor. The substrate maybe made of a plastic, glass, diamond, quartz, and/or any other suitablematerial. The dielectric mirror film may be applied to the substratesuch that the light emitted 1110 from the diamond 1102 is reflectedwithin the ellipsoidal reflector 1104. In some implementations, thedielectric mirror film may only reflect red light such that other colorsor wavelengths of light pass through the ellipsoidal reflector 1104. Forinstance, such a dielectric mirror film may permit transmission of greenwavelength light, such as from an excitation laser beam, through theellipsoidal reflector 1104 to the diamond 1102 to excite the diamond1102.

In some aspects, such as for precision sensors, the separation betweenthe diamond 1102 and the electronics of the photo detector 1120 can beextended, for example to several feet. In some implementations, the thindielectric mirror film is used in the ellipsoidal reflector 1104 toallow an RF antenna to be located inside the ellipsoidal reflector 1104.In some applications, the antenna may instead be outside of theellipsoidal reflector 1104.

FIG. 12 depicts an assembly 1200 with an example diamond 1202 havingnitrogen vacancies that is formed or machined into a reflectorconfiguration for a DNV light-collection apparatus. The diamond 1202 inthe present configuration is formed or machined into an ellipsoidalreflector and is a monolithic component that can be considered to bedivided into two portions, such as a reflector portion 1204 and aconcentrator portion 1206.

The diamond 1202 may have a dielectric mirror film coated on or appliedto the diamond 1202. The dielectric mirror film may be selected for thespecific frequency of interest. In some implementations, the thicknessof the dielectric mirror material may affect the specific frequency ofinterest. The dielectric mirror film may be applied such that the lightemitted 1210 from the nitrogen vacancies within the diamond 1202 isreflected within the reflector portion 1204 and concentrator portion1206 of the diamond 1202. In some implementations, the dielectric mirrorfilm may only reflect red light such that other colors or wavelengths oflight pass through the diamond 1202. For instance, such a dielectricmirror film may permit transmission of green wavelength light, such asfrom an excitation laser beam, through the dielectric mirror film to thenitrogen vacancies of the diamond 1202 to excite the nitrogen vacanciesof the diamond 1202.

The reflector portion 1204 of the diamond 1202 may internally reflectthe emitted light 1210 via the dielectric mirror film applied to thediamond 1202. Thus, the diamond 1202 internally reflects the red lightemitted 1210 from the diamond 1202 towards the concentrator portion1206. The concentrator portion 1206 also redirects the light emitted1210 by the nitrogen vacancies of the diamond 1202 toward a focus of theconcentrator portion 1206 of the diamond 1202. In the implementationshown, a photo detector 1220 is positioned to receive and measure thelight from the concentrator portion 1206. In some implementations, thephoto detector 1220 is positioned at the focus to receive the redirectedemitted light 1210. In some implementations the photo detector 1220 iscoupled and/or sealed to a portion of the diamond 1202, such as to theconcentrator portion 1206.

In some implementations, an optical filter, such as a red filter, may beapplied to and/or positioned on the photo detector 1220 to filter outlight except the relevant red light of interest.

In some implementations, a portion of the diamond 1202 may be formedwithout nitrogen vacancies. That is, for instance, one or more layersfor the diamond may be formed by chemical deposition without nitrogenvacancies. The one or more layers may be machined or formed for theconcentrator portion such that the emitted light reflected by thereflector portion 1204 is not reabsorbed by nitrogen vacancies whentravelling through the concentrator portion 1206 of the diamond 1202.

FIG. 13 depicts an assembly 1300 with an example diamond 1302 havingnitrogen vacancies and a parabolic reflector 1304 positioned about thediamond 1302 for a DNV light-collection apparatus. In someimplementations, the parabolic reflector 1304 can be a single monolithiccomponent. In some configurations, the parabolic reflector 1304 may becomposed of more than two components and can be coupled or otherwisepositioned to form the parabolic reflector 1304.

The diamond 1302 is positioned at a focus of the parabolic reflector1304. In some implementations, the diamond 1302 is positioned at thefocus using a mount for the diamond 1302. In other implementations, thediamond 1302 is positioned at the focus using a borehole through theparabolic reflector 1304. The borehole may be backfilled to seal thediamond 1302 in the parabolic reflector 1304.

The parabolic reflector 1304 may also include an opening to allow anexcitation laser beam to excite the diamond 1302, such as a greenexcitation laser beam. The opening may be positioned at any location forthe parabolic reflector 1304. When the diamond 1302 is excited (e.g., byapplying green light to the diamond 1302), then the parabolic reflector1304 reflects the red light emitted 1310 from the diamond 1302 towards aphoto detector 1320. In the implementation shown, a photo detector 1320is positioned to receive and measure the light from the parabolicreflector 1304. In some implementations the photo detector 1320 iscoupled and/or sealed to a portion of the parabolic reflector 1304. Insome implementations, the opening may be adjacent or proximate to thephoto detector 1320. In other implementations, the opening may beopposite the photo detector 1320. In still further configurations, theopening may be at any other angle and/or orientation relative to thephoto detector 1320.

In some implementations, an optical filter, such as a red filter, may beapplied to and/or positioned on the photo detector 1320 to filter outlight except the relevant red light of interest. Thus, the parabolicreflector 1304 is concatenated with a non-focusing concentrator that cancapture the emitted light from a light source (e.g., from the nitrogenvacancies of the diamond of a DNV sensor) to a single photo detector. Insome instances, the loss of emitted light can be limited to the lightloss due to the mount for the diamond and/or the small entrance for thegreen stimulation laser beam.

The foregoing solution provides high light collection efficiency tocollect the light emitted from the diamond 1302, while utilizing aparabolic reflector 1304 that may not require high precisionrefinements. Such a parabolic reflector 1304 may be a low cost solutionto increase the light collection efficiency, such as using a reflectivemirror component. In addition, the shape of the parabolic reflector 1304may separate the electronics of the photo detector 1320 from the diamond1302, which may decrease the magnetic interaction between theelectronics of the photo detector 1320 and the diamond 1302.

The parabolic reflector 1304 may, in some implementations, include asubstrate with a dielectric mirror film or coating applied to reflectthe emitted light 1310. The dielectric mirror film may be selected forthe specific frequency of interest. In some implementations, thethickness of the dielectric mirror material may affect the specificfrequency of interest. For instance, the substrate may possess a highclarity at a frequency of interest for the DNV sensor. The substrate maybe made of a plastic, glass, diamond, quartz, and/or any other suitablematerial. The dielectric mirror film may be applied to the substratesuch that the light emitted 1310 from the diamond 1302 is reflectedwithin the parabolic reflector 1304. In some implementations, thedielectric mirror film may only reflect red light such that other colorsor wavelengths of light pass through the parabolic reflector 1304. Forinstance, such a dielectric mirror film may permit transmission of greenwavelength light, such as from an excitation laser beam, through theparabolic reflector 1304 to the diamond 1302 to excite the diamond 1302.

In some aspects, such as for precision sensors, the separation betweenthe diamond 1302 and the electronics of the photo detector 1320 can beextended, for example to several feet. In some implementations, the thindielectric mirror film is used in the parabolic reflector 1304 to allowan RF antenna to be located inside the parabolic reflector 1304. In someapplications, the antenna may instead be outside of the parabolicreflector 1304.

FIG. 14 depicts an assembly 1400 with an example diamond 1402 havingnitrogen vacancies that is formed or machined into a reflectorconfiguration for a DNV light-collection apparatus. The diamond 1402 inthe present configuration is formed or machined into a parabolicreflector and is a monolithic component.

The diamond 1402 may have a dielectric mirror film coated on or appliedto the diamond 1402. The dielectric mirror film may be selected for thespecific frequency of interest. In some implementations, the thicknessof the dielectric mirror material may affect the specific frequency ofinterest. The dielectric mirror film may be applied such that the lightemitted 1410 from the nitrogen vacancies within the diamond 1402 isreflected within the diamond 1402. In some implementations, thedielectric mirror film may only reflect red light such that other colorsor wavelengths of light pass through the diamond 1402. For instance,such a dielectric mirror film may permit transmission of greenwavelength light, such as from an excitation laser beam, through thedielectric mirror film to the nitrogen vacancies of the diamond 1402 toexcite the nitrogen vacancies of the diamond 1402.

The parabolic reflector configuration for the diamond 1402 mayinternally reflect the emitted light 1410 via the dielectric mirror filmapplied to the diamond 1402. Thus, the diamond 1402 internally reflectsthe red light emitted 1410 from the diamond 1402 a photo detector 1420that is positioned to receive and measure the light emitted. In someimplementations the photo detector 1420 is coupled and/or sealed to aportion of the diamond 1402.

In some implementations, an optical filter, such as a red filter, may beapplied to and/or positioned on the photo detector 1420 to filter outlight except the relevant red light of interest.

In some implementations, a portion of the diamond 1402 may be formedwithout nitrogen vacancies. That is, for instance, one or more layersfor the diamond may be formed by chemical deposition without nitrogenvacancies. The one or more layers may be machined or formed near thejunction for the photo detector 1420 such that the emitted lightreflected by the parabolic reflector configuration of the diamond 1402is not reabsorbed by nitrogen vacancies when travelling through the oneor more layers of the diamond 1402.

FIG. 15 depicts another implementation of a parabolic reflectorconfiguration for an assembly 1500 for a DNV sensor. An example thindiamond 1502 having nitrogen vacancies may be inserted into a portion ofa parabolic reflector 1504 positioned about the diamond 1502 for a DNVlight-collection apparatus. In some implementations, the parabolicreflector 1504 can be a single monolithic component that is split intotwo portions to insert the thin diamond 1502. In some otherconfigurations, the parabolic reflector 1504 may be composed of morethan two components and can be coupled or otherwise positioned to formthe parabolic reflector 1504. In the implementation shown, the thindiamond 1502 is inserted parallel to (and in some instances along) anaxis of symmetry the parabolic reflector 1504. In implementationsutilizing an ellipsoidal reflector, the thin diamond 1502 may beinserted parallel to and/or along a major axis of the ellipsoidalreflector.

The parabolic reflector 1504 may also include an opening to allow anexcitation laser beam to excite the diamond 1502, such as a greenexcitation laser beam. The opening may be positioned at any location forthe parabolic reflector 1504. When the diamond 1502 is excited (e.g., byapplying green light to the diamond 1502), then the parabolic reflector1504 reflects the red light emitted 1510 from the diamond 1502 towards aphoto detector 1520. In the implementation shown, a photo detector 1520is positioned to receive and measure the light from the parabolicreflector 1504. In some implementations the photo detector 1520 iscoupled and/or sealed to a portion of the parabolic reflector 1504. Insome implementations, the opening may be adjacent or proximate to thephoto detector 1520. In other implementations, the opening may beopposite the photo detector 1520. In still further configurations, theopening may be at any other angle and/or orientation relative to thephoto detector 1520.

In some implementations, an optical filter, such as a red filter, may beapplied to and/or positioned on the photo detector 1520 to filter outlight except the relevant red light of interest. Thus, the parabolicreflector 1504 is concatenated with a non-focusing concentrator that cancapture the emitted light from a light source (e.g., from the nitrogenvacancies of the diamond of a DNV sensor) to a single photo detector. Insome instances, the loss of emitted light can be limited to the lightloss due to the mount for the diamond and/or the small entrance for thegreen stimulation laser beam.

The foregoing solution provides high light collection efficiency tocollect the light emitted from the diamond 1502, while utilizing aparabolic reflector 1504 that may not require high precisionrefinements. Such a parabolic reflector 1504 may be a low cost solutionto increase the light collection efficiency, such as using a reflectivemirror component. In addition, the shape of the parabolic reflector 1504may separate the electronics of the photo detector 1520 from the diamond1502, which may decrease the magnetic interaction between theelectronics of the photo detector 1520 and the diamond 1502.

The parabolic reflector 1504 may, in some implementations, include asubstrate with a dielectric mirror film or coating applied to reflectthe emitted light 1510. The dielectric mirror film may be selected forthe specific frequency of interest. In some implementations, thethickness of the dielectric mirror material may affect the specificfrequency of interest. For instance, the substrate may possess a highclarity at a frequency of interest for the DNV sensor. The substrate maybe made of a plastic, glass, diamond, quartz, and/or any other suitablematerial. The dielectric mirror film may be applied to the substratesuch that the light emitted 1510 from the diamond 1502 is reflectedwithin the parabolic reflector 1504. In some implementations, thedielectric mirror film may only reflect red light such that other colorsor wavelengths of light pass through the parabolic reflector 1504. Forinstance, such a dielectric mirror film may permit transmission of greenwavelength light, such as from an excitation laser beam, through theparabolic reflector 1504 to the diamond 1502 to excite the diamond 1502.

In some aspects, such as for precision sensors, the separation betweenthe diamond 1502 and the electronics of the photo detector 1520 can beextended, for example to several feet. In some implementations, the thindielectric mirror film is used in the parabolic reflector 1504 to allowan RF antenna to be located inside the parabolic reflector 1504. In someapplications, the antenna may instead be outside of the parabolicreflector 1504.

FIG. 16 depicts another implementation of a parabolic reflectorconfiguration for an assembly 1600 for a DNV sensor. An example thindiamond 1602 having nitrogen vacancies may be inserted into a portion ofa parabolic reflector 1604 positioned about the diamond 1602 for a DNVlight-collection apparatus. In some implementations, the parabolicreflector 1604 can be a single monolithic component that is split intotwo portions to insert the thin diamond 1602. In some otherconfigurations, the parabolic reflector 1604 may be composed of morethan two components and can be coupled or otherwise positioned to formthe parabolic reflector 1604. In the implementation shown, the thindiamond 1602 is inserted perpendicular to an axis of symmetry theparabolic reflector 1604. In implementations utilizing an ellipsoidalreflector, the thin diamond 1602 may be inserted parallel to and/oralong a minor axis of the ellipsoidal reflector. In someimplementations, the thin diamond 1602 is positioned at a focus of theparabolic reflector 1604.

The parabolic reflector 1604 may also include an opening to allow anexcitation laser beam to excite the diamond 1602, such as a greenexcitation laser beam. The opening may be positioned at any location forthe parabolic reflector 1604. When the diamond 1602 is excited (e.g., byapplying green light to the diamond 1602), then the parabolic reflector1604 reflects the red light emitted 1610 from the diamond 1602 towards aphoto detector 1620. In the implementation shown, a photo detector 1620is positioned to receive and measure the light from the parabolicreflector 1604. In some implementations the photo detector 1620 iscoupled and/or sealed to a portion of the parabolic reflector 1604. Insome implementations, the opening may be adjacent or proximate to thephoto detector 1620. In other implementations, the opening may beopposite the photo detector 1620. In still further configurations, theopening may be at any other angle and/or orientation relative to thephoto detector 1620.

In some implementations, an optical filter, such as a red filter, may beapplied to and/or positioned on the photo detector 1620 to filter outlight except the relevant red light of interest. Thus, the parabolicreflector 1604 is concatenated with a non-focusing concentrator that cancapture the emitted light from a light source (e.g., from the nitrogenvacancies of the diamond of a DNV sensor) to a single photo detector. Insome instances, the loss of emitted light can be limited to the lightloss due to the mount for the diamond and/or the small entrance for thegreen stimulation laser beam.

The foregoing solution provides high light collection efficiency tocollect the light emitted from the diamond 1602, while utilizing aparabolic reflector 1604 that may not require high precisionrefinements. Such a parabolic reflector 1604 may be a low cost solutionto increase the light collection efficiency, such as using a reflectivemirror component. In addition, the shape of the parabolic reflector 1604may separate the electronics of the photo detector 1620 from the diamond1602, which may decrease the magnetic interaction between theelectronics of the photo detector 1620 and the diamond 1602.

The parabolic reflector 1604 may, in some implementations, include asubstrate with a dielectric mirror film or coating applied to reflectthe emitted light 1610. The dielectric mirror film may be selected forthe specific frequency of interest. In some implementations, thethickness of the dielectric mirror material may affect the specificfrequency of interest. For instance, the substrate may possess a highclarity at a frequency of interest for the DNV sensor. The substrate maybe made of a plastic, glass, diamond, quartz, and/or any other suitablematerial. The dielectric mirror film may be applied to the substratesuch that the light emitted 1610 from the diamond 1602 is reflectedwithin the parabolic reflector 1604. In some implementations, thedielectric mirror film may only reflect red light such that other colorsor wavelengths of light pass through the parabolic reflector 1604. Forinstance, such a dielectric mirror film may permit transmission of greenwavelength light, such as from an excitation laser beam, through theparabolic reflector 1604 to the diamond 1602 to excite the diamond 1602.

In some aspects, such as for precision sensors, the separation betweenthe diamond 1602 and the electronics of the photo detector 1620 can beextended, for example to several feet. In some implementations, the thindielectric mirror film is used in the parabolic reflector 1604 to allowan RF antenna to be located inside the parabolic reflector 1604. In someapplications, the antenna may instead be outside of the parabolicreflector 1604.

FIG. 17 depicts an assembly 1700 for a DNV sensor that incorporates theassembly 1400 of FIG. 15 where the diamond 1402 is formed or machinedinto a parabolic configuration. The assembly 1700 includes the photodetector 1420 coupled to and/or positioned to receive the emitted light1410 from the diamond 1402. The diamond 1402 includes the dielectricmirror film applied to the diamond 1402 to reflect the emitted red light1410 within the diamond 1402. In some implementations, the dielectricmirror film may only reflect red light such that other colors orwavelengths of light pass through the diamond 1402. For instance, such adielectric mirror film may permit transmission of green wavelength light1710, such as from an excitation laser beam, through the dielectricmirror film to the nitrogen vacancies of the diamond 1402 to excite thenitrogen vacancies of the diamond 1402. The assembly 1700 includesmicrowave coils about the diamond 1402 such that, if the diamond 1402 isirradiated with microwaves at a certain frequency, then the diamond willcease and/or reduce the emission of red light. A microwave off isperformed for the DNV sensor prior to illumination of the diamond 1402to emit the red light 1410. When the microwave frequency is moved to adifferent frequency, then the red light emitted is dimmed and thefrequency is related to the strength of the magnetic field the DNVsensor is within.

In some implementations, the green light 1710 from the green laser maybe applied through a fiber, rather than the free air, to the diamond1402. In some implementations, the entire apparatus of FIG. 17 may be ascompact as ˜2 mm. The assembly of the subject technology may be used ina number of applications, for example, in all areas of magnetometry,where DNV magnetometers are employed.

FIG. 18 depicts another implementation of a reflector configuration foran assembly 1800 for a DNV sensor that includes a waveguide 1830positioned within the reflector to direct light to a diamond 1802 havingnitrogen vacancies. An example diamond 1802 having nitrogen vacanciesmay be inserted into a portion of a reflector 1804 positioned about thediamond 1802 for a DNV light-collection apparatus. In someimplementations, the reflector 1804 may be a parabolic reflector or anellipsoidal reflector. The reflector 1804 can be a single monolithiccomponent or can be a shell component with a fill, such as plastic orfiber optic material, or without a fill (e.g., empty). In theimplementation shown, a waveguide 1830 is formed or inserted along anaxis of symmetry of the parabolic reflector 1804. In otherimplementations, the waveguide 1830 is formed or inserted along a majoraxis of an ellipsoidal reflector 1804. The waveguide 1830 may be a fiberoptic component and/or may simply be a material having a differingrefractive index than the reflector 1804 and/or the fill within thereflector 1804.

The diamond 1802 is positioned at an end of the waveguide 1830 such thatan excitation beam, such as green laser light, can be transmitted viathe waveguide 1830 to the diamond 1802. When the diamond 1802 is excited(e.g., by applying green light to the diamond 1802), then the reflector1804 reflects the red light emitted 1810 from the diamond 1802 towards aphoto detector 1820. In the implementation shown, a photo detector 1820is positioned to receive and measure the light from the reflector 1804.In some implementations the photo detector 1820 is coupled and/or sealedto a portion of the reflector 1804. In some implementations, an openingfor transmitting the excitation beam is through the photo detector 1820such that the excitation beam can be transmitted via the waveguide 1830to the diamond 1802. In other implementations, an emitter to emit lightto excite the nitrogen vacancy of the diamond 1802, such as theexcitation beam, may be provided at a first end of the waveguide 1830with the diamond 1802 at a second end of the waveguide 1830. In someimplementations, the emitter may be formed and/or positioned within orat a center of the photo detector 1820 to generate and transmit theexcitation beam along the waveguide 1830 to the diamond 1802. The photodetector 1820 and emitter may be positioned on a single substrate. Thus,a single chip can include both the photo detector 1820 and the emitterfor the excitation beam such that both the illumination and collectioncan be provided on the single chip.

In some implementations, an optical filter, such as a red filter, may beapplied to and/or positioned on the photo detector 1820 to filter outlight except the relevant red light of interest. Thus, the reflector1804 is concatenated with a non-focusing concentrator that can capturethe emitted light from a light source (e.g., from the nitrogen vacanciesof the diamond of a DNV sensor) to a single photo detector. In someinstances, the loss of emitted light can be limited to the light lossdue to the mount for the diamond and/or any emitted light that travelsback down the waveguide 1830.

The foregoing solution provides high light collection efficiency tocollect the light emitted from the diamond 1802, while utilizing areflector 1804 that may not require high precision refinements. Such areflector 1804 may be a low cost solution to increase the lightcollection efficiency, such as using a reflective mirror component. Inaddition, the shape of the parabolic reflector 1804 may separate theelectronics of the photo detector 1820 and/or emitter from the diamond1802, which may decrease the magnetic interaction between theelectronics of the photo detector 1820 and/or emitter and the diamond1802.

The reflector 1804 may, in some implementations, include a substratewith a dielectric mirror film or coating applied to reflect the emittedlight 1810. The dielectric mirror film may be selected for the specificfrequency of interest. In some implementations, the thickness of thedielectric mirror material may affect the specific frequency ofinterest. For instance, the substrate may possess a high clarity at afrequency of interest for the DNV sensor. The substrate may be made of aplastic, glass, diamond, quartz, and/or any other suitable material. Thedielectric mirror film may be applied to the substrate such that thelight emitted 1810 from the diamond 1802 is reflected within thereflector 1804. In some implementations, the dielectric mirror film mayonly reflect red light such that other colors or wavelengths of lightpass through the reflector 1804.

In some aspects, such as for precision sensors, the separation betweenthe diamond 1802 and the electronics of the photo detector 1820 can beextended, for example to several feet. In some implementations, the thindielectric mirror film is used in the reflector 1804 to allow an RFantenna to be located inside the reflector 1804. In some applications,the antenna may instead be outside of the reflector 1804.

FIG. 19 depicts an implementation of a process 1900 to form a DNVsensor. The process 1900 includes providing a diamond having a nitrogenvacancy (block 1902), machining a portion of the diamond to form areflector (block 1904), positioning a photo detector relative to thediamond to receive light emitted from the diamond (block 1906), and/orapplying a dielectric mirror film coat to a portion of the diamond(block 1908). In some implementations, the process 1900 may includesimple providing a diamond having a nitrogen vacancy (block 1902) andapplying a dielectric mirror film coat to a portion of the diamond(block 1908).

In some implementations, the machining of the diamond to form areflector (block 1904) may machine a portion of the diamond to form aparabolic shape, an ellipsoidal shape, and/or any other suitable shape.In some implementations, a layer of the diamond may not have nitrogenvacancies.

FIG. 20 depicts another process 2000 to form a DNV sensor. The process2000 includes providing a diamond having a nitrogen vacancy and areflector (block 2002), positioning the diamond within the reflectorsuch that the reflector reflects a portion of the light from the diamond(block 2004), and/or positioning a photo detector relative to thediamond to receive light emitted from the diamond (block 2006).

In some implementations, the reflector is monolithic and the diamond ispositioned within a borehole of the monolithic reflector. In someimplementations, the borehole may be backfilled. In someimplementations, the reflector may be formed from two or more pieces andpositioning the diamond within the reflector includes inserting thediamond between the two or more pieces. In some instances, the diamondmay be substantially flat, such as in the configuration shown in FIGS.15-16. The two or more pieces of the reflector may be parabolic inshape. The diamond may be positioned parallel to an axis of symmetry ofthe parabolic reflector or may be positioned perpendicular to the axisof symmetry. In other implementations, the two or more pieces of thereflector may be ellipsoidal in shape. The diamond may be positionedparallel to a major axis of the ellipsoidal reflector or may bepositioned parallel to a minor axis of the ellipsoidal reflector. Insome further implementations, positioning the diamond within thereflector may include casting the reflector about the diamond.

FIG. 21 is a diagram illustrating an example of a system 2100 forimplementing some aspects of the subject technology. In someimplementations, the system 2100 may be a processing system forprocessing the data output from a photo detector of the implementationsdescribe in reference to FIGS. 11-19. The system 2100 includes aprocessing system 2102, which may include one or more processors or oneor more processing systems. A processor can be one or more processors.The processing system 2102 may include a general-purpose processor or aspecific-purpose processor for executing instructions and may furtherinclude a machine-readable medium 2119, such as a volatile ornon-volatile memory, for storing data and/or instructions for softwareprograms. The instructions, which may be stored in a machine-readablemedium 2110 and/or 2119, may be executed by the processing system 2102to control and manage access to the various networks, as well as provideother communication and processing functions. The instructions may alsoinclude instructions executed by the processing system 2102 for varioususer interface devices, such as a display 2112 and a keypad 2114. Theprocessing system 2102 may include an input port 2122 and an output port2124. Each of the input port 2122 and the output port 2124 may includeone or more ports. The input port 2122 and the output port 2124 may bethe same port (e.g., a bi-directional port) or may be different ports.

The processing system 2102 may be implemented using software, hardware,or a combination of both. By way of example, the processing system 2102may be implemented with one or more processors. A processor may be ageneral-purpose microprocessor, a microcontroller, a Digital SignalProcessor (DSP), an Application Specific Integrated Circuit (ASIC), aField Programmable Gate Array (FPGA), a Programmable Logic Device (PLD),a controller, a state machine, gated logic, discrete hardwarecomponents, or any other suitable device that can perform calculationsor other manipulations of information.

A machine-readable medium can be one or more machine-readable media.Software shall be construed broadly to mean instructions, data, or anycombination thereof, whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.Instructions may include code (e.g., in source code format, binary codeformat, executable code format, or any other suitable format of code).

Machine-readable media (e.g., 2119) may include storage integrated intoa processing system such as might be the case with an ASIC.Machine-readable media (e.g., 2110) may also include storage external toa processing system, such as a Random Access Memory (RAM), a flashmemory, a Read Only Memory (ROM), a Programmable Read-Only Memory(PROM), an Erasable PROM (EPROM), registers, a hard disk, a removabledisk, a CD-ROM, a DVD, or any other suitable storage device. Thoseskilled in the art will recognize how best to implement the describedfunctionality for the processing system 2102. According to one aspect ofthe disclosure, a machine-readable medium is a computer-readable mediumencoded or stored with instructions and is a computing element, whichdefines structural and functional interrelationships between theinstructions and the rest of the system, which permit the instructions'functionality to be realized. Instructions may be executable, forexample, by the processing system 2102 or one or more processors.Instructions can be, for example, a computer program including code forperforming methods of the subject technology.

A network interface 2116 may be any type of interface to a network(e.g., an Internet network interface), and may reside between any of thecomponents shown in FIG. 21 and coupled to the processor via the bus2104.

A device interface 2118 may be any type of interface to a device and mayreside between any of the components shown in FIG. 21. A deviceinterface 2118 may, for example, be an interface to an external device(e.g., USB device) that plugs into a port (e.g., USB port) of the system2100. In some implementations, the device interface 2118 may be aninterface to the apparatus of FIGS. 10-18, where some or all of theanalysis of the detected red light by the photo detector electronics ishandled by the processing system 2102.

The foregoing description is provided to enable a person skilled in theart to practice the various configurations described herein. While thesubject technology has been particularly described with reference to thevarious figures and configurations, it should be understood that theseare for illustration purposes only and should not be taken as limitingthe scope of the subject technology.

One or more of the above-described features and applications may beimplemented as software processes that are specified as a set ofinstructions recorded on a computer readable storage medium(alternatively referred to as computer-readable media, machine-readablemedia, or machine-readable storage media). When these instructions areexecuted by one or more processing unit(s) (e.g., one or moreprocessors, cores of processors, or other processing units), they causethe processing unit(s) to perform the actions indicated in theinstructions. In one or more implementations, the computer readablemedia does not include carrier waves and electronic signals passingwirelessly or over wired connections, or any other ephemeral signals.For example, the computer readable media may be entirely restricted totangible, physical objects that store information in a form that isreadable by a computer. In one or more implementations, the computerreadable media is non-transitory computer readable media, computerreadable storage media, or non-transitory computer readable storagemedia.

In one or more implementations, a computer program product (also knownas a program, software, software application, script, or code) can bewritten in any form of programming language, including compiled orinterpreted languages, declarative or procedural languages, and it canbe deployed in any form, including as a stand-alone program or as amodule, component, subroutine, object, or other unit suitable for use ina computing environment. A computer program may, but need not,correspond to a file in a file system. A program can be stored in aportion of a file that holds other programs or data (e.g., one or morescripts stored in a markup language document), in a single filededicated to the program in question, or in multiple coordinated files(e.g., files that store one or more modules, sub programs, or portionsof code). A computer program can be deployed to be executed on onecomputer or on multiple computers that are located at one site ordistributed across multiple sites and interconnected by a communicationnetwork.

While the above discussion primarily refers to microprocessor ormulti-core processors that execute software, one or more implementationsare performed by one or more integrated circuits, such as applicationspecific integrated circuits (ASICs) or field programmable gate arrays(FPGAs). In one or more implementations, such integrated circuitsexecute instructions that are stored on the circuit itself.

In one or more implementations, the subject technology is directed tomethod and systems for an efficient collection of fluorescence (e.g.,red light) emitted by the NV centers of a DNV sensor. In some aspects,the subject technology may be used in various markets, including forexample and without limitation, advanced sensors and materials andstructures.

Precision Position Encoder/Sensor Using Nitrogen Vacancy Diamond

A position sensor system may include a position sensor that includes amagnetic field sensor. The magnetic field sensor may be a DNV magneticfield sensor capable of resolving a magnetic field vector of the typedescribed above. The high sensitivity of the DNV magnetic field sensorcombined with an appropriate position encoder component is capable ofresolving both a discrete position and a proportionally determinedposition between discrete positions. The position sensor system has asmall size, light weight, and low power requirement.

As shown in FIG. 22, the position sensor 2220 may be part of a systemthat also includes an actuator 2210 and a sensor component 2230. Theactuator 2210 may be connected to the position sensor 2220 by anyappropriate attachment means 2214, such as a rod or shaft. The actuatormay be any actuator that produces the desired motion, such as anelectro-mechanical actuator. The position sensor 2220 may be connectedto the sensor component 2230 by any appropriate attachment means 2224,such as a rod or shaft. A controller 2240 may be included in the systemand connected to the position sensor 2220 and optionally the actuator2210 by electronic interconnects 2222 and 2212, respectively. Thecontroller may be configured to receive a measured position from theposition sensor 2220 and activate or deactivate the actuator to positionthe sensor 2230 in a desired position. According to one embodiment thecontroller may be on the same substrate as the magnetic field sensor ofthe position sensor. The controller may include a processor and amemory.

The position sensor may be a rotary position sensor. FIG. 23 depicts arotary position sensor system that includes a rotary actuator 2380 thatis configured to produce a rotation of a sensor 2390. A rotary positionencoder 2310 is connected to the rotary actuator 2380 by a connectionmeans 2382, such as a rod or shaft. A connection means 2392 is alsoprovided between the rotary position encoder 2310 and the sensor 2390. Aposition sensor head 2320 is located to measure the magnetic field ofmagnetic elements located on the rotary position encoder 2310. Theposition sensor head 2320 is aligned with magnetic elements located onthe rotary position encoder 2310 at a distance, r, from the center ofthe rotary position encoder. A surface of the rotary position encoder2310 that includes magnetic elements is shown in FIG. 24. The center2440 of the rotary position encoder 2310 may be configured to attach toa connection means 2392, 2394 that connects the rotary position encoder2310 to the actuator 2320 or the sensor 2390. Magnetic elements, such asuniform coarse magnetic elements 2434 and tapered fine magnetic elements2432, may be disposed on the surface of the rotary position encoder 2310along an arc 2436 at a distance, r, from the center of the rotaryposition encoder. The magnetic elements on the rotary position encoder2310 may be located on only a portion of the arc, as shown in FIG. 24,or around an entirety of the arc forming a circle of magnetic elements.

The spacing between the magnetic elements on the rotary position encoder2310 correlates to a discrete angular rotation, θ. The distance betweenmagnetic elements associated with the discrete angular rotation, θ,increases as r increases. The sensitivity of the magnetic field sensorsemployed in the position sensor allows r to be reduced while maintaininga high degree of precision for the angular position of the rotaryposition encoder. The rotary position encoder may have an r on the orderof mm, such as an r of 1 mm to about 30 mm, or about 5 mm to about 20mm. The rotary position encoder allows for the measurement of a rotaryposition with a precision of 0.5 micro-radians.

The position sensor may be a linear position sensor. As shown in FIG.25, the linear position sensor system includes a linear actuator 2580that is configured to produce linear motion of the linear positionencoder 2510 and sensor 2590. The linear position encoder 2510 may beconnected to the linear actuator by a connecting means 2582, such as arod or shaft. The linear position encoder 2510 may be connected to thesensor 2590 by a connecting means 2592, such as a rod or shaft. Aposition sensor head 2520 is located to measure the magnetic fieldproduced by magnetic elements disposed on the linear position encoder.In some cases, a mechanical linkage, such as a lever arm, may beutilized to multiply the change in position of the linear positionencoder for an associated movement of the sensor. The linear positionsensor may have a sensitivity that allows a change in position on theorder of hundreds of nanometers to be resolved, such as a positionchange of 500 nm.

The magnetic elements may be arranged on the linear or rotary positionencoder in any appropriate configuration. As shown in FIG. 26, themagnetic elements may include both uniform coarse magnetic elements 2634and tapered fine magnetic elements 2632. The uniform coarse magneticelements 2634 may have an influence on the local magnetic field that isat least two orders of magnitude greater than the maximum influence ofthe tapered fine magnetic elements 2634. The coarse magnetic elements2634 may be formed on the position encoder by any suitable process.According to one embodiment, a polymer loaded with magnetic material maybe utilized to form the uniform coarse magnetic elements. The amount ofmagnetic material that may be included in the coarse magnetic elementsis limited by potential interference with other elements in the system.

The tapered fine magnetic elements may be formed by any suitable processon the position encoder. According to one embodiment, a polymer loadedwith magnetic material may be utilized to form the tapered fine magneticelements. The loading of the magnetic material in the polymer may beincreased to produce a magnetic field gradient from a first end of thetapered fine magnetic element to a second end of the tapered finemagnetic element. Alternatively, the geometric size of the tapered finemagnetic element may be increased to create the desired magnetic fieldgradient. A magnetic field gradient of the tapered fine magnetic elementmay be about 10 nT/mm. The tapered fine magnetic elements 2632 as shownin FIG. 26 allow positions between the coarse magnetic elements 2634 tobe accurately resolved. The position encoder on which the magneticelements are disposed may be formed from any appropriate material, suchas a ceramic, glass, polymer, or non-magnetic metal material.

The size of the magnetic elements is limited by manufacturingcapabilities. The magnetic elements on the position encoder may havegeometric features on the order of nanometers, such as about 5 nm.

FIG. 27 depicts an alternate magnetic element arrangement that may beemployed when the additional precision provided by the tapered finemagnetic elements is not required. The magnetic element arrangement ofFIG. 27 includes only coarse magnetic elements 2634. FIG. 13 depicts amagnetic element arrangement that does not include coarse magneticelements. A similar effect to the coarse magnetic elements 2634 may beachieved by utilizing the transitions between the maximum of the taperedfine magnetic elements 2632 and the minimum of the adjacent tapered finemagnetic elements as indicators in much the same way that the coarsemagnetic elements shown in FIGS. 26 and 27 indicate a discrete change inposition. While FIGS. 26-18 depict the magnetic element arrangements inlinear form, similar magnetic element arrangements may be applied to arotary position encoder.

According to an alternative embodiment, a single tapered magneticelement may be employed. Such an arrangement may be especially suitablefor an application where only a small position range is required, as fora larger position range the increase in magnetic field with theincreasing gradient of the magnetic element may interfere with othercomponents of the position sensor system. The use of a single taperedmagnetic element may allow a position to be determined without firstinitializing the position sensor by setting the position encoder to aknown position. The ability of the magnetic field sensor to resolve amagnetic field vector may allow a single magnetic field sensor to beemployed in the position sensor head when a single tapered fine magneticelement is utilized on the position encoder.

The position sensor head 2620 may include a plurality of magnetic fieldsensors, as shown in FIG. 29. For magnetic element arrangementsincluding more than one element, at least two magnetic field sensors2624 and 2622 may be utilized in the position head sensor. The magneticfield sensors may be separated by a distance, a. The distance, a,between the magnetic sensors 2622 and 2624 may be less than thedistance, d, between the coarse magnetic elements 2634. According to oneembodiment, the relationship between the spacing of the magnetic fieldsensors and the spacing of the coarse magnetic elements may be 0.1d<a<d.As shown in FIG. 29, the position sensor head 2620 may include a thirdand fourth magnetic field sensor. The magnetic field sensors in theposition sensor head may be DNV magnetic field sensors of the typedescribed above.

The magnetic field sensor arrangement in the position sensor head 2620depicted in FIG. 29 allows the direction of movement of the positionencoder to be determined. As shown in FIG. 30, the spacing between themagnetic field sensors 2624 and 2622 produces a delayed response to themagnetic field elements as the position encoder moves. The difference inmeasured magnetic field for each magnetic field sensor allows adirection of the movement of the position encoder to be determined, asfor any given position of the position encoder a different outputmagnetic field will be measured by each magnetic field sensor. Theincreasing portion of the plots in FIG. 30 is produced by the taperedfine magnetic element and the square peak is produced by the coarsemagnetic element. These measured magnetic fields may be utilized todetermine the change in position of the position encoder, and therebythe sensor connected to the position encoder.

The controller of the position sensor system may be programmed todetermine the position of position encoder, and thereby the sensorconnected thereto, utilizing the output from the magnetic field sensors.As shown in FIG. 31, the controller may include a line transection logic3102 function that determines when the coarse magnetic elements havepassed the magnetic sensor. The output from two magnetic field sensorsB1 and B2 may be utilized to determine the direction of the positionchange based on the order in which a coarse magnetic element isencountered by the magnetic field sensors, and to count the number ofcoarse magnetic elements measured by the magnetic field sensors. Eachcoarse magnetic element adds a known amount of position change due tothe known spacing between the coarse magnetic elements on the positionencoder. An element gradient logic processing function 3100 isprogrammed in the controller to determine the position between coarsemagnetic elements based on the magnetic field signal produced by thetapered fine magnetic elements located between the coarse magneticelements. As shown in Step 3104 of FIG. 31, the element gradient logicprocessing 3100 is utilized only when the line transection logicdetermines that the position is between coarse magnetic elements, orlines. In the case that the position is determined to be between coarsemagnetic elements, a position correction, δθ, is calculated based on themagnetic field associated with the tapered fine magnetic elements. Theposition correction is then added to the sum of the position changecalculated from the number of coarse magnetic elements that werecounted. A final position may be calculated by adding the calculatedposition change to a starting position of the position encoder. Thelogic processing in the controller may be conducted by analog or digitalcircuits.

The position sensor may be employed in a method for controlling theposition of the position encoder. The method includes determining amovement direction required to reach a desired position, and activatingthe actuator to produce the desired movement. The position sensor isemployed to monitor the change in position of the position encoder, anddetermine when to deactivate the actuator and stop the change inposition. The change in position may be stopped once the desiredposition is reached. The method may additionally include initializingthe position sensor system by moving the position encoder to a knownstarting point. The end position of the position encoder may bedetermined after the deactivation of the actuator, and the end positionmay be stored in a memory of the position sensor controller as astarting position for future movement.

The ability of the position sensor system to resolve positions betweenthe coarse magnetic elements of the position encoder provides manypractical benefits. For example, the position of the position encoder,and associated sensor, may be known with more precision while reducingthe size, weight and power requirements of the position sensor system.Additionally, position control systems that offer resolution of discreteposition movements can result in dithering when a desired position isbetween two discrete position values. Dithering can result in unwantedvibration and overheating of the actuator as the control systemrepeatedly tries to reach the desired position.

The characteristics of the position sensor system described above makeit especially suitable for applications where precision, size, weight,and power requirements are important considerations. The position sensorsystem is well suited for astronautic applications, such as on spacevehicles. The position sensor system is also applicable to robot arms,3-d mills, machine tools, and X-Y tables.

The position sensor system may be employed to control the position of avariety of sensors and other devices. Non-limiting examples of sensorsthat could be controlled with the position sensor system are opticalsensors.

Communication Via a Magnio

Radio waves can be used as a carrier for information. Thus, atransmitter can modulate radio waves at one location, and a receiver atanother location can detect the modulated radio waves and demodulate thesignals to receive the information. Many different methods can be usedto transmit information via radio waves. However, all such methods useradio waves as a carrier for the information being transmitted.

However, radio waves are not well suited for all communication methods.For example, radio waves can be greatly attenuated by some materials.For example, radio waves do not generally travel well through water.Thus, communication through water can be difficult using radio waves.Similarly, radio waves can be greatly attenuated by the earth. Thus,wireless communication through the earth, for example for coal or othermines, can be difficult. It is often difficult to communicate wirelesslyvia radio waves from a metal enclosure. The strength of a radio wavesignal can also be reduced as the radio wave passes through materialssuch as walls, trees, or other obstacles. Additionally, communicationvia radio waves is widely used and understood. Thus, secretcommunication using radio waves requires complex methods and devices tomaintain the secrecy of the information.

According to some embodiments described herein, wireless communicationis achieved without using radio waves as a carrier for information.Rather, modulated magnetic fields can be used to transmit information.For example, a transmitter can include a coil or inductor. When currentpasses through the coil, a magnetic field is generated around the coil.The current that passes through the coil can be modulated, therebymodulating the magnetic field. Accordingly, information converted into amodulated electrical signal (e.g., the modulated current through thecoil) can be used to transfer the information into a magnetic field. Amagnetometer can be used to monitor the magnetic field. The modulatedmagnetic field can, therefore, be converted into traditional electricalsystems (e.g., using current to transfer information). Thus, acommunications signal can be converted into a magnetic field and aremote receiver (e.g., a magnetometer) can be used to retrieve thecommunication from the modulated magnetic field.

A diamond with a nitrogen vacancy (DNV) can be used to measure amagnetic field. DNV sensors generally have a quick response to magneticfields, consume little power, and are accurate. Diamonds can bemanufactured with nitrogen vacancy (NV) centers in the lattice structureof the diamond. When the NV centers are excited by light, for examplegreen light, and microwave radiation, the NV centers emit light of adifferent frequency than the excitation light. For example, green lightcan be used to excite the NV centers, and red light can be emitted fromthe NV centers. When a magnetic field is applied to the NV centers, thefrequency of the light emitted from the NV centers changes.Additionally, when the magnetic field is applied to the NV centers, thefrequency of the microwaves at which the NV centers are excited changes.Thus, by shining a green light (or any other suitable color) through aDNV and monitoring the light emitted from the DNV and the frequencies ofmicrowave radiation that excite the NV centers, a magnetic field can bemonitored.

NV centers in a diamond are oriented in one of four spin states. Eachspin state can be in a positive direction or a negative direction. TheNV centers of one spin state do not respond the same to a magnetic fieldas the NV centers of another spin state. A magnetic field vector has amagnitude and a direction. Depending upon the direction of the magneticfield at the diamond (and the NV centers), some of the NV centers willbe excited by the magnetic field more than others based on the spinstate of the NV centers.

FIGS. 32A and 32B are graphs illustrating the frequency response of aDNV sensor in accordance with an illustrative embodiment. FIGS. 32A and32B are meant to be illustrative only and not meant to be limiting.FIGS. 32A and 32B plot the frequency of the microwaves applied to a DNVsensor on the x-axis versus the amount of light of a particularfrequency (e.g., red) emitted from the diamond. FIG. 32A is thefrequency response of the DNV sensor with no magnetic field applied tothe diamond, and FIG. 32B is the frequency response of the DNV sensorwith a seventy gauss (G) magnetic field applied to the diamond.

As shown in FIG. 32A, when no magnetic field is applied to the DNVsensor, there are two notches in the frequency response. With nomagnetic field applied to the DNV sensor, the spin states are notresolvable. That is, with no magnetic field, the NV centers with variousspin states are equally excited and emit light of the same frequency.The two notches shown in FIG. 32A are the result of the positive andnegative spin directions. The frequency of the two notches is the axialzero field splitting parameter.

When a magnetic field is applied to the DNV sensor, the spin statesbecome resolvable in the frequency response. Depending upon theexcitation by the magnetic field of NV centers of a particular spinstate, the notches corresponding to the positive and negative directionsseparate on the frequency response graph. As shown in FIG. 32B, when amagnetic field is applied to the DNV sensor, eight notches appear on thegraph. The eight notches are four pairs of corresponding notches. Foreach pair of notches, one notch corresponds to a positive spin state andone notch corresponds to a negative spin state. Each pair of notchescorresponds to one of the four spin states of the NV centers. The amountby which the pairs of notches deviate from the axial zero fieldsplitting parameter is dependent upon how strongly the magnetic fieldexcites the NV centers of the corresponding spin states.

As mentioned above, the magnetic field at a point can be characterizedwith a magnitude and a direction. By varying the magnitude of themagnetic field, all of the NV centers will be similarly affected. Usingthe graph of FIG. 32A as an example, the ratio of the distance from 2.87GHz of one pair to another will remain the same when the magnitude ofthe magnetic field is altered. As the magnitude is increased, each ofthe notch pairs will move away from 2.87 GHz at a constant rate,although each pair will move at a different rate than the other pairs.

When the direction of the magnetic field is altered, however, the pairsof notches do not move in a similar manner to one another. FIG. 33A is adiagram of NV center spin states in accordance with an illustrativeembodiment. FIG. 33A conceptually illustrates the four spin states ofthe NV centers. The spin states are labeled NV A, NV B, NV C, and NV D.Vector 3301 is a representation of a first magnetic field vector withrespect to the spin states, and Vector 3302 is a representation of asecond magnetic field vector with respect to the spin states. Vector3301 and vector 3302 have the same magnitude, but differ in direction.Accordingly, based on the change in direction, the various spin stateswill be affected differently depending upon the direction of the spinstates.

FIG. 33B is a graph illustrating the frequency response of a DNV sensorin response to a changed magnetic field in accordance with anillustrative embodiment. The frequency response graph illustrates thefrequency response of the DNV sensor from the magnetic fieldcorresponding to vector 3301 and to vector 3302. As shown in FIG. 33B,the notches corresponding to the NV A and NV D spin states moved closerto the axial zero field splitting parameter from vector 3301 to vector3302, the negative (e.g., lower frequency notch) notch of the NV C spinstate moved away from the axial zero field splitting parameter, thepositive (e.g., high frequency notch) of the NV C spin state stayedessentially the same, and the notches corresponding to the NV B spinstate increased in frequency (e.g., moved to the right in the graph).Thus, by monitoring the changes in frequency response of the notches,the DNV sensor can determine the direction of the magnetic field.

Additionally, magnetic fields of different directions can be modulatedsimultaneously and each of the modulations can be differentiated oridentified by the DNV sensor. For example, a magnetic field in thedirection of NV A can be modulated with a first pattern, a magneticfield in the direction of NV B can be modulated with a second pattern, amagnetic field in the direction of NV C can be modulated with a thirdpattern, and a magnetic field in the direction of NV D can be modulatedwith a fourth pattern. The movement of the notches in the frequencyresponse corresponding to the various spin states can be monitored todetermine each of the four patterns.

However, in some embodiments, the direction of the magnetic fieldcorresponding to the various spin states of a DNV sensor of a receivermay not be known by the transmitter. In such embodiments, by monitoringat least three of the spin states, messages transmitted on two magneticfields that are orthogonal to one another can be deciphered. Similarly,by monitoring the frequency response of the four spin states, messagestransmitted on three magnetic fields that are orthogonal to one anothercan be deciphered. Thus, in some embodiments, two or three independentsignals can be transmitted simultaneously to a receiver that receivesand deciphers the two or three signals. Such embodiments can be amultiple-input multiple-output (MIMO) system. Diversity in thepolarization of the magnetic field channels provides a full rank channelmatrix even through traditionally keyhole channels. In an illustrativeembodiment, a full rank channel matrix allows MIMO techniques toleverage all degrees of freedom (e.g., three degrees of polarization).Using a magnetic field to transmit information circumvents the keyholeeffect that propagating a radio frequency field can have.

FIG. 34 is a block diagram of a magnetic communication system inaccordance with an illustrative embodiment. An illustrative magniosystem 3400 includes input data 3405, a 3410, a transmitter 3445, amodulated magnetic field 3450, a magnetometer 3455, a magnio receiver3460, and output data 3495. In alternative embodiments, additional,fewer, and/or different elements may be used.

In an illustrative embodiment, input data 3405 is input into the magniosystem 3400, transmitted wirelessly, and the output data 3495 isgenerated at a location remote from the generation of the input data3405. In an illustrative embodiment, the input data 3405 and the outputdata 3495 contain the same information.

In an illustrative embodiment, input data 3405 is sent to the magniotransmitter 3410. The magnio transmitter 3410 can prepare theinformation received in the input data 3405 for transmission. Forexample, the magnio transmitter 3410 can encode or encrypt theinformation in the input data 3405. The magnio transmitter 3410 can sendthe information to the transmitter 3445.

The transmitter 3445 is configured to transmit the information receivedfrom the magnio transmitter 3410 via one or more magnetic fields. Thetransmitter 3445 can be configured to transmit the information on one,two, three, or four magnetic fields. That is, the transmitter 3445 cantransmit information via a magnetic field oriented in a first direction,transmit information via a magnetic field oriented in a seconddirection, transmit information via a magnetic field oriented in a thirddirection, and/or transmit information via a magnetic field oriented ina fourth direction. In some embodiments in which the transmitter 3445transmits information via two or three magnetic fields, the magneticfields can be orthogonal to one another. In alternative embodiments, themagnetic fields are not orthogonal to one another.

The transmitter 3445 can be any suitable device configured to create amodulated magnetic field. For example, the transmitter 3445 can includeone or more coils. Each coil can be a conductor wound around a centralaxis. For example, in embodiments in which the information istransmitted via three magnetic fields, the transmitter 3445 can includethree coils. The central axis of each coil can be orthogonal to thecentral axis of the other coils.

The transmitter 3445 generates the modulated magnetic field 3450. Themagnetometer 3455 can detect the modulated magnetic field 3450. Themagnetometer 3455 can be located remotely from the transmitter 3445. Forexample, with a current of about ten Amperes through a coil (e.g., thetransmitter) and with a magnetometer magnetometer 3455 with asensitivity of about one hundred nano-Tesla, a message can be sent,received, and recovered in fill with several meters between thetransmitter and receiver and with the magnetometer magnetometer 3455inside of a Faraday cage. The magnetometer 3455 can be configured tomeasure the modulated magnetic field 3450 along three or fourdirections. As discussed above, a magnetometer 3455 using a DNV sensorcan measure the magnetic field along four directions associated withfour spin states. The magnetometer 3455 can transmit information, suchas frequency response information, to the magnio receiver 3460.

The magnio receiver 3460 can analyze the information received from themagnetometer 3455 and decipher the information in the signals. Themagnio receiver 3460 can reconstitute the information contained in theinput data 3405 to produce the output data 3495.

In an illustrative embodiment, the magnio transmitter 3410 includes adata packet generator 3415, an outer encoder 3420, an interleaver 3425,an inner encoder 3430, an interleaver 3435, and an output packetgenerator 3440. In alternative embodiments, additional, fewer, and/ordifferent elements may be used. The various components of the magniotransmitter 310 are illustrated in FIG. 34 as individual components andare meant to be illustrative only. However, in alternative embodiments,the various components may be combined. Additionally, the use of arrowsis not meant to be limiting with respect to the order or flow ofoperations or information. Any of the components of the magniotransmitter 3410 can be implemented using hardware and/or software.

The input data 3405 can be sent to the data packet generator 3415. In anillustrative embodiment, the input data 3405 is a series or stream ofbits. The data packet generator 3415 can break up the stream of bitsinto packets of information. The packets can be any suitable size. In anillustrative embodiment, the data packet generator 3415 includesappending a header to the packets that includes transmission managementinformation. In an illustrative embodiment the header can includeinformation used for error detection, such as a checksum. Any suitableheader may be used. In some embodiments, the input data 3405 is notbroken into packets.

The stream of data generated by the data packet generator 3415 can besent to the outer encoder 3420. The outer encoder 3420 can encrypt orencode the stream using any suitable cipher or code. Any suitable typeof encryption can be used such as symmetric key encryption. In anillustrative embodiment, the encryption key is stored on memoryassociated with the magnio transmitter 3410. In an illustrativeembodiment, the magnio transmitter 3410 may not include the outerencoder 3420. For example, the messages may not be encrypted. In anillustrative embodiment, the outer encoder 3420 separates the streaminto multiple channels. In an illustrative embodiment, the outer encoderouter encoder 3420 performs forward error correction (FEC). In someembodiments, the forward error correction dramatically increases thereliability of transmissions for a given power level.

In an illustrative embodiment, the encoded stream from the outer encoder3420 is sent to the interleaver 3425. In an illustrative embodiment, theinterleaver 3425 interleaves bits within each packet of the stream ofdata. In such an embodiment, each packet has the same bits, but the bitsare shuffled according to a predetermined pattern. Any suitableinterleaving method can be used. In an alternative embodiment, thepackets are interleaved. In such an embodiment, the packets are shuffledaccording to a predetermined pattern. In some embodiments, the magniotransmitter 3410 may not include the interleaver 3425.

In some embodiments, interleaving data can be used to prevent loss of asequence of data. For example, if a stream of bits are in sequentialorder and there is a communication loss during a portion of the stream,there is a relatively large gap in the information corresponding to thelost bits. However, if the bits were interleaved (e.g., shuffled), oncethe stream is de-interleaved (e.g., unshuffled) at the receiver, thelost bits are not grouped together but are spread across the sequentialbits. In some instances, if the lost bits are spread across the message,error correction can be more successful in determining what the lostbits were supposed to be.

In an illustrative embodiment, the interleaved stream from theinterleaver 3425 is sent to the inner encoder 3430. The inner encoder3430 can encrypt or encode the stream using any suitable cipher or code.Any suitable type of encryption can be used such as symmetric keyencryption. In an illustrative embodiment, the encryption key is storedon memory associated with the magnio transmitter 3410. In anillustrative embodiment, the magnio transmitter 3410 may not include theinner encoder 3430. In an illustrative embodiment, the inner encoder3430 and the outer encoder 3420 perform different functions. Forexample, the inner encoder 3430 can use a deep convolutional code andcan perform most of the forward error correction, and the outer encodercan be used to correct residual errors and can use a different codingtechnique from the inner encoder 3430 (e.g., a block-parity basedencoding technique).

In an illustrative embodiment, the encoded stream from the inner encoder3430 is sent to the interleaver 3435. In an illustrative embodiment, theinterleaver 3435 interleaves bits within each packet of the stream ofdata. In such an embodiment, each packet has the same bits, but the bitsare shuffled according to a predetermined pattern. Any suitableinterleaving method can be used. In an alternative embodiment, thepackets are interleaved. In such an embodiments, the packets areshuffled according to a predetermined pattern. In an illustrativeembodiment, interleaving the data spreads out burst-like errors acrossthe signal, thereby facilitating the decoding of the message. In someembodiment, the magnio transmitter 3410 may not include the interleaver3435.

In an illustrative embodiment, the interleaved stream from theinterleaver 3435 is sent to the output packet generator 3440. The outputpacket generator 3440 can generate the packets that will be transmitted.For example, the output packet generator 3440 may append a header to thepackets that includes transmission management information. In anillustrative embodiment the header can include information used forerror detection, such as a checksum. Any suitable header may be used.

In an illustrative embodiment, the output packet generator 3440 appendsa synchronization sequence to each of the packets. For example, asynchronization sequence can be added to the beginning of each packet.The packets can be transmitted on multiple channels. In such anembodiment, each channel is associated with a unique synchronizationsequence. The synchronization sequence can be used to decipher thechannels from one another, as is discussed in greater detail below withregard to the magnio receiver 3460.

In an illustrative embodiment, the output packet generator 3440modulates the waveform to be transmitted. Any suitable modulation can beused. In an illustrative embodiment, the waveform is modulateddigitally. In some embodiments, minimum shift keying can be used tomodulate the waveform. For example, non-differential minimum shift keycan be used. In an illustrative embodiment, the waveform has acontinuous phase. That is, the waveform does not have phasediscontinuities. In an illustrative embodiment, the waveform issinusoidal in nature.

In an illustrative embodiment, the modulated waveform is sent to thetransmitter 3445. In an illustrative embodiment, multiple modulatedwaveforms are sent to the transmitter 3445. As mentioned above, two,three, or four signals can be transmitted simultaneously via magneticfields with different directions. In an illustrative embodiment, threemodulated waveforms are sent to the transmitter 3445. Each of thewaveforms can be used to modulate a magnetic field, and each of themagnetic fields can be orthogonal to one another.

The transmitter 3445 can use the received waveforms to produce themodulated magnetic field 3450. The modulated magnetic field 3450 can bea combination of multiple magnetic fields of different directions. Thefrequency used to modulate the modulated magnetic field 3450 can be anysuitable frequency. In an illustrative embodiment, the carrier frequencyof the modulated magnetic field 3450 can be 10 kHz. In alternativeembodiments, the carrier frequency of the modulated magnetic field 3450can be less than or greater than 10 kHz. In some embodiments, thecarrier frequency can be modulated to plus or minus the carrierfrequency. That is, using the example in which the carrier frequency is10 kHz, the carrier frequency can be modulated down to 0 Hz and up to 20kHz. In alternative embodiments, any suitable frequency band can beused.

FIGS. 35A and 35B show the strength of a magnetic field versus frequencyin accordance with an illustrative embodiment. FIGS. 35A and 35B aremeant to be illustrative only and not meant to be limiting. In someinstances, the magnetic spectrum is relatively noisy. As shown in FIG.35A, the noise over a large band (e.g., 0-200 kHz) is relatively high.Thus, communicating over such a large band may be difficult. FIG. 35Billustrates the noise over a smaller band (e.g., 1-3 kHz). As shown inFIG. 35B, the noise over a smaller band is relatively low. Thus,modulating the magnetic field across a smaller band of frequencies canbe less noisy and more effective. In an illustrative embodiment, themagnio transmitter 3410 can monitor the magnetic field and determine asuitable frequency to modulate the magnetic fields to reduce noise. Thatis, the magnio transmitter 3410 can find a frequency that has a highsignal to noise ratio. In an illustrative embodiment, the magniotransmitter 3410 determines a frequency band that has noise that isbelow a predetermined threshold.

In an illustrative embodiment, the magnio receiver 3460 includes thedemodulator 3465, the de-interleaver 3470, the soft inner decoder 3475,the de-interleaver 3480, the outer decoder 3485, and the output datagenerator 3490. In alternative embodiments, additional, fewer, and/ordifferent elements may be used. For example, the magnio receiver 3460can include the magnetometer 3455 in some embodiments. The variouscomponents of the magnio receiver 3460 are illustrated in FIG. 34 asindividual components and are meant to be illustrative only. However, inalternative embodiments, the various components may be combined.Additionally, the use of arrows is not meant to be limiting with respectto the order or flow of operations or information. Any of the componentsof the magnio receiver 3460 can be implemented using hardware and/orsoftware.

The magnetometer 3455 is configured to measure the modulated magneticfield 3450. In an illustrative embodiment, the magnetometer 3455includes a DNV sensor. The magnetometer 3455 can monitor the modulatedmagnetic field 3450 in up to four directions. As illustrated in FIG. 2A,the magnetometer 3455 can be configured to measure the magnetometer 3455in one or more of four directions that are tetrahedronally arranged. Asmentioned above, the magnetometer 3455 can monitor n+1 directions wheren is the number of channels that the transmitter 3445 transmits on. Forexample, the transmitter 3445 can transmit on three channels, and themagnetometer 3455 can monitor four directions. In an alternativeembodiment, the transmitter 3445 can transmit via the same number ofchannels (e.g., four) as directions that the magnetometer 3455 monitors.

The magnetometer 3455 can send information regarding the modulatedmagnetic field 3450 to the demodulator 3465. The demodulator 3465 cananalyze the received information and determine the direction of themagnetic fields that were used to create the modulated magnetic field3450. That is, the demodulator 3465 can determine the directions of thechannels that the transmitter 3445 transmitted on. As mentioned above,the transmitter 3445 can transmit multiple streams of data, and eachstream of data is transmitted on one channel. Each of the streams ofdata can be preceded by a unique synchronization sequence. In anillustrative embodiment, the synchronization sequence includes 1023bits. In alternative embodiments, the synchronization sequence includesmore than or fewer than 1023 bits. Each of the streams can betransmitted simultaneously such that each of the channels aretime-aligned with one another. The demodulator 3465 can monitor themagnetic field in multiple directions simultaneously. Based on thesynchronization sequence, which is known to the magnio receiver 3460,the demodulator 3465 can determine the directions corresponding to thechannels of the transmitter 3445. When the streams of synchronizationsequences are time-aligned, the demodulator 3465 can monitor themodulated magnetic field 3450 to determine how the multiple channelsmixed. Once the demodulator 3465 determines how the various channels aremixed, the channels can be demodulated.

For example, the transmitter 3445 transmits on three channels, with eachchannel corresponding to an orthogonal direction. Each channel is usedto transmit a stream of information. For purposes of the example, thechannels are named “channel A,” “channel B,” and “channel C.” Themagnetometer 3455 monitors the modulated magnetic field 3450 in fourdirections. The demodulator 3465 can monitor for three signals inorthogonal directions. For purposes of the example, the signals can benamed “signal 1,” “signal 2,” and “signal 3.” Each of the signals cancontain a unique, predetermined synchronization sequence. Thedemodulator 3465 can monitor the modulated magnetic field 3450 for thesignals to be transmitted on the channels. There is a finite number ofpossible combinations that the signals can be received at themagnetometer 3455. For example, signal 1 can be transmitted in adirection corresponding to channel A, signal 2 can be transmitted in adirection corresponding to channel B, and signal 3 can be transmitted ina direction corresponding to channel C. In another example, signal 2 canbe transmitted in a direction corresponding to channel A, signal 3 canbe transmitted in a direction corresponding to channel B, and signal 1can be transmitted in a direction corresponding to channel C, etc. Themodulated magnetic field 3450 of the synchronization sequence for eachof the possible combinations that the signals can be received at themagnetometer 3455 can be known by the demodulator 3465. The demodulator3465 can monitor the output of the magnetometer 3455 for each of thepossible combinations. Thus, when one of the possible combinations isrecognized by the demodulator 3465, the demodulator 3465 can monitor foradditional data in directions associated with the recognizedcombination. In another example, the transmitter 3445 transmits on twochannels, and the magnetometer 3455 monitors the modulated magneticfield 3450 in three directions.

The demodulated signals (e.g., the received streams of data from each ofthe channels) is sent to the de-interleaver 3470. The de-interleaver3470 can undo the interleaving of the interleaver 3435. Thede-interleaved streams of data can be sent to the soft inner decoder3475, which can undo the encoding of the inner encoder 3430. Anysuitable decoding method can be used. For example, in an illustrativeembodiment the inner encoder 3430 uses a three-way, soft-decision turbodecoding function. In an alternative embodiment, a two-way,soft-decision turbo decoding function may be used. For example, theexpected cluster positions for signal levels are learned by the magnioreceiver 3460 during the synchronization portion of the transmission.When the payload/data portion of the transmission is processed by themagnio receiver 3460, distances from all possible signal clusters to theobserved signal value are computed for every bit position. The bits ineach bit position are determined by combining the distances with statetransition probabilities to find the best path through a “trellis.” Thepath through the trellis can be used to determine the most likely bitsthat were communicated.

The decoded stream can be transmitted to the de-interleaver 3480. Thede-interleaver 3480 can undo the interleaving of the interleaver 3425.The de-interleaved stream can be sent to the outer decoder 3485. In anillustrative embodiment, the outer decoder 3485 undoes the encoding ofthe outer encoder 3420. The unencoded stream of information can be sentto the output data generator 3490. In an illustrative embodiment, theoutput data generator 3490 undoes the packet generation of data packetgenerator 3415 to produce the output data 3495.

FIG. 36 is a block diagram of a computing device in accordance with anillustrative embodiment. An illustrative computing device 3600 includesa memory 3610, a processor 3605, a transceiver 3615, a user interface3620, and a power source 3625. In alternative embodiments, additional,fewer, and/or different elements may be used. The computing device 3600can be any suitable device described herein. For example, the computingdevice 3600 can be a desktop computer, a laptop computer, a smartphone,a specialized computing device, etc. The computing device 3600 can beused to implement one or more of the methods described herein.

In an illustrative embodiment, the memory 3610 is an electronic holdingplace or storage for information so that the information can be accessedby the processor 3605. The memory 3610 can include, but is not limitedto, any type of random access memory (RAM), any type of read only memory(ROM), any type of flash memory, etc. such as magnetic storage devices(e.g., hard disk, floppy disk, magnetic strips, etc.), optical disks(e.g., compact disk (CD), digital versatile disk (DVD), etc.), smartcards, flash memory devices, etc. The computing device 3600 may have oneor more computer-readable media that use the same or a different memorymedia technology. The computing device 3600 may have one or more drivesthat support the loading of a memory medium such as a CD, a DVD, a flashmemory card, etc.

In an illustrative embodiment, the processor 3605 executes instructions.The instructions may be carried out by a special purpose computer, logiccircuits, or hardware circuits. The processor 3605 may be implemented inhardware, firmware, software, or any combination thereof. The term“execution” is, for example, the process of running an application orthe carrying out of the operation called for by an instruction. Theinstructions may be written using one or more programming language,scripting language, assembly language, etc. The processor 3605 executesan instruction, meaning that it performs the operations called for bythat instruction. The processor 3605 operably couples with the userinterface 3620, the transceiver 3615, the memory 3610, etc. to receive,to send, and to process information and to control the operations of thecomputing device 3600. The processor 3605 may retrieve a set ofinstructions from a permanent memory device such as a ROM device andcopy the instructions in an executable form to a temporary memory devicethat is generally some form of RAM. An illustrative computing device3600 may include a plurality of processors that use the same or adifferent processing technology. In an illustrative embodiment, theinstructions may be stored in memory 3610.

In an illustrative embodiment, the transceiver 3615 is configured toreceive and/or transmit information. In some embodiments, thetransceiver 3615 communicates information via a wired connection, suchas an Ethernet connection, one or more twisted pair wires, coaxialcables, fiber optic cables, etc. In some embodiments, the transceiver3615 communicates information via a wireless connection usingmicrowaves, infrared waves, radio waves, spread spectrum technologies,satellites, etc. The transceiver 3615 can be configured to communicatewith another device using cellular networks, local area networks, widearea networks, the Internet, etc. In some embodiments, one or more ofthe elements of the computing device 3600 communicate via wired orwireless communications. In some embodiments, the transceiver 3615provides an interface for presenting information from the computingdevice 3600 to external systems, users, or memory. For example, thetransceiver 3615 may include an interface to a display, a printer, aspeaker, etc. In an illustrative embodiment, the transceiver 3615 mayalso include alarm/indicator lights, a network interface, a disk drive,a computer memory device, etc. In an illustrative embodiment, thetransceiver 3615 can receive information from external systems, users,memory, etc.

In an illustrative embodiment, the user interface 3620 is configured toreceive and/or provide information from/to a user. The user interface3620 can be any suitable user interface. The user interface 3620 can bean interface for receiving user input and/or machine instructions forentry into the computing device 3600. The user interface 3620 may usevarious input technologies including, but not limited to, a keyboard, astylus and/or touch screen, a mouse, a track ball, a keypad, amicrophone, voice recognition, motion recognition, disk drives, remotecontrollers, input ports, one or more buttons, dials, joysticks, etc. toallow an external source, such as a user, to enter information into thecomputing device 3600. The user interface 3620 can be used to navigatemenus, adjust options, adjust settings, adjust display, etc.

The user interface 3620 can be configured to provide an interface forpresenting information from the computing device 3600 to externalsystems, users, memory, etc. For example, the user interface 3620 caninclude an interface for a display, a printer, a speaker,alarm/indicator lights, a network interface, a disk drive, a computermemory device, etc. The user interface 3620 can include a color display,a cathode-ray tube (CRT), a liquid crystal display (LCD), a plasmadisplay, an organic light-emitting diode (OLED) display, etc.

In an illustrative embodiment, the power source 3625 is configured toprovide electrical power to one or more elements of the computing device3600. In some embodiments, the power source 3625 includes an alternatingpower source, such as available line voltage (e.g., 120 Voltsalternating current at 60 Hertz in the United States). The power source3625 can include one or more transformers, rectifiers, etc. to convertelectrical power into power useable by the one or more elements of thecomputing device 3600, such as 1.5 Volts, 8 Volts, 12 Volts, 24 Volts,etc. The power source 3625 can include one or more batteries.

Method for Resolving Natural Sensor Ambiguity for DNV Direction FindingApplications

Natural Ambiguity of NV Center Magnetic Sensor System

The NV center magnetic sensor that operates as described above iscapable of resolving a magnetic field to an unsigned vector. As shown inFIG. 37, due to the symmetry of the peaks for the m_(s)=−1 and them_(s)=+1 spin states around the zero splitting photon energy thestructure of the DNV material produces a measured fluorescence spectrumas a function of RF frequency that is the same for a positive and anegative magnetic field acting on the DNV material. The symmetry of thefluorescence spectra makes the assignment of a sign to the calculatedmagnetic field vector unreliable. The natural ambiguity introduced tothe magnetic field sensor is undesirable in some applications, such asmagnetic field based direction sensing.

In some circumstances, real world conditions allow the intelligentassignment of a sign to the unsigned magnetic field vector determinedfrom the fluorescence spectra described above. If a known bias field isused that is much larger than the signal of interest, the sign of themagnetic field vector may be determine by whether the total magneticfield, cumulative of the bias field and the signal of interest,increases or decreases. If the magnetic sensor is employed to detectsubmarines from a surface ship, assigning the calculated magnetic fieldvector a sign that would place a detected submarine above the surfaceship would be nonsensical. Alternatively, where the sign of the vectoris not important a sign can be arbitrarily assigned to the unsignedvector.

It is possible to unambiguously determine a magnetic field vector with aDNV magnetic field sensor. The method of determining the signed magneticfield vector may be performed with a DNV magnetic field sensor of thetype shown in FIG. 6 and described above. In general, the recovery ofthe vector may be achieved as described in U.S. application Ser. No.15/003,718, filed Jan. 21, 2016, titled “APPARATUS AND METHOD FORRECOVERY OF THREE DIMENSIONAL MAGNETIC FIELD FROM A MAGNETIC DETECTIONSYSTEM”, which issued as U.S. Pat. No. 9,541,610 on Jan. 10, 2017, andis incorporated by reference herein in its entirety.

As shown in FIG. 2, the energy levels of the ms=−1 and the ms=+1 spinstates are different. For this reason, the relaxation times from theexcited triplet states (3E) to the excited intermediate singlet state(A) for electrons with the ms=−1 and the ms=+1 spin states are not thesame. The difference in relaxation times for electrons of ms=−1 and thems=+1 spin states is on the order of picoseconds or nanoseconds. It ispossible to measure the difference in relaxation times for the electronswith the ms=−1 and the ms=+1 spin states by utilizing pulsed RFexcitation such that the inequality in the relaxation times accumulatesover a large number of electron cycles, producing a difference inobserved relaxation times on the order of microseconds.

As described above, the application of RF excitation to the DNV materialproduces a decrease in fluorescence intensity at the resonant RFfrequencies for the ms=−1 and the ms=+1 spin states. For this reason, atRF frequencies that excite electrons to the ms=−1 and the ms=+1 spinstates, an equilibrium fluorescence intensity will be lower than theequilibrium fluorescence intensity in the absence of the applied RFexcitation. The time it takes to transition from the equilibriumfluorescence intensity in the absence of RF excitation to theequilibrium fluorescence intensity with the application of RF excitationmay be employed to calculate an “equilibration time.”

An “equilibration time” as utilized herein refers to the time betweenthe start of an RF excitation pulse and when a predetermined percentageof the equilibrium fluorescence intensity is achieved. The predeterminedamount of the equilibrium fluorescence at which the equilibration timeis calculated may be about 20% to about 80% of the equilibriumfluorescence, such as about 30%, 40%, 50%, 60%, or 70% of theequilibrium fluorescence. The equilibration time as shown in FIGS. 38,40 and 41 is actually a decay time, as the fluorescence intensity isactually decreasing in the presence of the RF excitation, but has beeninverted for the sake of clarity.

A shown in FIG. 38, the fluorescence intensity of the DNV materialvaries with the application of a pulsed RF excitation source. When theRF pulse is in the “on” state, the electrons decay through anon-fluorescent path and a relatively dark equilibrium fluorescence isachieved. The absence of the RF excitation, when the pulse is in the“off” state, results in a relatively bright equilibrium fluorescence.The transition between the two fluorescence equilibrium states is notinstantaneous, and the measurement of the equilibration time at apredetermined value of fluorescence intensity provides a repeatableindication of the relaxation time for the electrons at the RF excitationfrequency.

The difference in the relaxation time between the electrons of the ms=−1and the ms=+1 spin states may be measured due to the different RFexcitation resonant frequencies for each spin state. As shown in FIG.39, a fluorescence intensity spectra of the DNV material measured as afunction of RF excitation frequency includes four Lorentzian pairs, onepair for each crystallographic plane of the DNV material. The peaks in aLorentzian pair correspond to a ms=−1 and a ms=+1 spin state. Byevaluating the equilibration time for each peak in a Lorentzian pair,the peak which corresponds to the higher energy state may be identified.The higher energy peak provides a reliable indication of the sign of themagnetic field vector.

The Lorentzian pair of the fluorescence spectra which are locatedfurthest from the zero splitting energy may be selected to calculate theequilibration time. These peaks include the least signal interferenceand noise, allowing a more reliable measurement. The preferredLorentzian pair is boxed in FIG. 39.

A plot of the fluorescence intensity for a single RF pulse as a functionof time is shown in FIG. 40. The frequency of the pulsed RF excitationis selected to be the maximum value for each peak in the Lorentzianpair. The other conditions for the measurement of an equilibration timefor each peak in the Lorentzian pair are held constant. As shown in FIG.41, the peaks of the Lorentzian pair have an equilibration time whencalculated to 60% of the equilibrium intensity value that isdistinguishable. The RF pulse duration may be set such that the desiredpercentage of the equilibrium fluorescence intensity is achieved foreach “on” portion of the pulse, and the full “bright” equilibriumintensity is achieved during the “off” portion of the pulse.

The equilibrium fluorescence intensity under the application of the RFexcitation may be set by any appropriate method. According to someembodiments, the RF excitation may be maintained until the intensitybecomes constant, and the constant intensity may be considered theequilibrium intensity value utilized to calculate the equilibrationtime. Alternatively, the equilibrium intensity may be set to theintensity at the end of an RF excitation pulse. According to otherembodiments, a decay constant may be calculated based on the measuredfluorescence intensity and a theoretical data fit employed to determinethe equilibrium intensity value.

The peak in the Lorentzian pair that exhibits the higher measuredequilibration time is associated with the higher energy level electronspin state. For this reason, the peak of the Lorentzian pair with thelonger equilibration time is assigned the ms=+1 spin state, and theother peak in the Lorentzian pair is assigned the ms=−1 spin state. Thesigns of the peaks in the other Lorentzian pairs in the fluorescencespectra of the DNV material as a function of RF frequency may then beassigned, and the signed magnetic field vector calculated.

To demonstrate that the equilibration time of each peak in a Lorentzianpair does indeed vary with magnetic field direction, the equilibrationtime for a single peak in a Lorentzian pair was measured under both apositive and a negative magnetic bias field which were otherwiseequivalent. As shown in FIG. 42, a real and measurable difference inequilibration time was observed between the opposite bias fields.

The method of determining a sign of a magnetic field vector with a DNVmagnetic sensor described herein may be performed with the DNV magneticfield sensor shown in FIG. 6. No additional hardware is required.

The controller of the magnetic field sensor may be programmed todetermine the location of peaks in a fluorescence spectra of a DNVmaterial as a function of RF frequency. The equilibration time for thepeaks of a Lorentzian pair located the furthest from the zero fieldenergy may then be calculated. The controller may be programmed toprovide a pulsed RF excitation energy by controlling a RF excitationsource and also control an optical excitation source to excite the DNVmaterial with continuous wave optical excitation. The resulting opticalsignal received at the optical detector may be analyzed by thecontroller to determine the equilibration time associated with each peakin the manner described above. The controller may be programmed toassign a sign to each peak based on the measured equilibration time. Thepeak with the greater measured equilibration time may be assigned them_(s)=+1 spin state.

The method of assigning a sign to a magnetic field vector describedabove may also be applied to magnetic field sensors based onmagneto-optical defect center materials other than DNV.

The DNV magnetic field sensor described herein that produces a signedmagnetic field vector may be especially useful in applications in whichthe direction of a measured magnetic field is important. For example,the DNV magnetic field sensor may be employed in magnetic field basednavigation or positioning systems.

Hydrophone

FIGS. 43A and 43B are diagrams illustrating hydrophone systems inaccordance with illustrative embodiments. An illustrative system 4300includes a hull 4305 and a magnetometer 4310. In alternativeembodiments, additional, fewer, or different elements can be used. Forexample, an acoustic transmitter can be used to generate one or moreacoustic signals. In the embodiments in which a transmitter is not used,the system 4300 can be used as a passive sonar system. For example, thesystem 4300 can be used to detect sounds created by something other thana transmitter (e.g., a ship, a boat, an engine, a mammal, ice movement,etc.).

In an illustrative embodiment, the hull 4305 is the hull of a vesselsuch as a ship or a boat. The hull 4305 can be any suitable material,such as steel or painted steel. In alternative embodiments, themagnetometer 4310 is installed in alternative structures such as a bulkhead or a buoy.

As illustrated in FIG. 43A, the magnetometer 4310 can be located withinthe 4305. In the embodiment, the magnetometer 4310 is located at theouter surface of the hull 4305. In alternative embodiments, themagnetometer 4310 can be located at any suitable location. For example,magnetometer 4310 can be located near the middle of the hull 4305, at aninner surface of the hull 4305, or on an inner or outer surface of thehull 4305.

In an illustrative embodiment, the magnetometer 4310 is a magnetometerwith a diamond with NV centers. In an illustrative embodiment, themagnetometer 4310 has a sensitivity of about 0.1 micro Tesla. Inalternative embodiments, the magnetometer 4310 has a sensitivity ofgreater than or less than 0.1 micro Tesla.

In the embodiment illustrated in FIG. 43A, sound waves 4315 propagatethrough a fluid with dissolved ions, such as sea water. As the soundwaves 4315 move the ions in the fluid, the ions create a magnetic field.For example, as the ions move within the magnetic field of the Earth,the ions create a magnetic field that is detectable by the magnetometer4310. In another embodiment, a magnetic field source such as a permanentmagnet or an electromagnet can be used. The movement of the ions withrespect to the source of the magnetic field (e.g., the Earth) createsthe magnetic field detectable by the magnetometer 4310.

In an illustrative embodiment, the sound waves 4315 travel through seawater. The density of dissolved ions in the fluid near the magnetometer4310 depends on the location in the sea that the magnetometer 4310 is.For example, some locations have a lower density of dissolved ions thanothers. The higher the density of the dissolved ions, the greater thecombined magnetic field created by the movement of the ions. In anillustrative embodiment, the strength of the combined magnetic field canbe used to determine the density of the dissolved ions (e.g., thesalinity of the sea water).

In an illustrative embodiment, the hull 4305 is the hull of a ship thattravels through the sea water. As noted above, the movement of the ionsrelative to the source magnetic field can be measured by themagnetometer 4310. Thus, the magnetometer 4310 can be used to detect andmeasure the sound waves 4315 as the magnetometer 4310 moves through thesea water and as the magnetometer 4310 is stationary in the sea water.

In an illustrative embodiment, the magnetometer 4310 can measure themagnetic field caused by the moving ions in any suitable direction. Forexample, the magnetometer 4310 can measure the magnetic field caused bythe movement of the ions when the sound waves 4315 is perpendicular tothe hull 4305 or any other suitable angle. In some embodiments, themagnetometer 4310 measures the magnetic field caused by the movement ofions caused by sound waves 4315 that are parallel to the surface of thehull 4305.

An illustrative system 4350 includes the hull 4305 and an array ofmagnetometers 4355. In alternative embodiments, additional, fewer,and/or different elements can be used. For example, although FIG. 43Billustrates four magnetometers 4355 are used. In alternativeembodiments, the system 4350 can include fewer than four magnetometers4355 or more than magnetometers 4355. The array of the magnetometers4355 can be used to increase the sensitivity of the hydrophone. Forexample, by using multiple magnetometers 4355, the hydrophone hasmultiple measurement points.

The array of magnetometers 4355 can be arranged in any suitable manner.For example, the magnetometers 4355 can be arranged in a line. Inanother example, the magnetometers 4355 can be arranged in a circle, inconcentric circles, in a grid, etc. The array of magnetometers 4355 canbe uniformly arranged (e.g., the same distance from one another) ornon-uniformly arranged. The array of magnetometers 4355 can be used todetermine the direction from which the sound waves 4315 travel. Forexample, the sound waves 4315 can cause ions near one the bottommagnetometer of the magnetometers 4355 of the embodiment illustrated inthe system 4350 to create a magnetic field before the sound waves 4315cause ions near the top magnetometer of the magnetometers 4355. Thus, itcan be determined that the sound waves 4315 travels from the bottom tothe top of FIG. 43B.

In an illustrative embodiment, the magnetometer 4310 or themagnetometers 4355 can determine the angle that the sound waves 4315travel relative to the magnetometer 4310 based on the direction of themagnetic field caused by the movement of the ions. For example,individual magnetometers of the magnetometers 4355 can each beconfigured to measure the magnetic field of the ions in a differentdirection. Principles of beamforming can be used to determine thedirection of the magnetic field. In alternative embodiments, anysuitable magnetometer 4310 or magnetometers 4355 can be used todetermine the direction of the magnetic field and/or the direction ofthe acoustic signal.

Magnetic Navigation Methods and Systems Utilizing Power Grid andCommunication Network

In some embodiments, methods and configurations are disclosed fordiamond nitrogen-vacancy (DNV) magnetic navigation via powertransmission and distribution lines. The characteristic magneticsignature of human infrastructure provides context for navigation. Forexample, power lines, which have characteristic magnetic signatures, canserve as roads and highways for mobile platforms (e.g., UASs). Travel inrelatively close proximity to power lines may allow stealthy transit,may provide the potential for powering the mobile platform itself, andmay permit point-to-point navigation both over long distances and localroutes.

Some implementations can include one or more magnetic sensors, amagnetic navigation database, and a feedback loop that controls the UASposition and orientation. DNV magnetic sensors and related systems andmethods may provide high sensitivity magnetic field measurements. TheDNV magnetic systems and methods can also be low cost, space, weight,and power (C-SWAP) and benefit from a fast settling time. The DNVmagnetic field measurements may allow UAS systems to align themselveswith the power lines, and to rapidly move along the power-lineinfrastructure routes. The subject solution can enable navigation inpoor visibility conditions and/or in GPS-denied environments. Suchmagnetic navigation allows for UAS operation in close proximity to powerlines facilitating stealthy transit. DNV-based magnetic systems andmethods can be approximately 100 times smaller than conventional systemsand can have a reaction time that that is approximately 100,000 timesfaster than other systems.

FIG. 44 is a diagram illustrating an example of UAS 4402 navigationalong power lines 4404, 4406, and 4408, according to someimplementations of the subject technology. The UAS 4402 can exploit thedistinct magnetic signatures of power lines for navigation such that thepower lines can serve as roads and highways for the UAS 4402 without theneed for detailed a priori knowledge of the route magneticcharacteristics. As shown in FIG. 45A, a ratio of signal strength of twomagnetic sensors, A and B (4410 and 4412 in FIG. 44), attached to wingsof the UAS 4402, varies as a function of distance, x, from a center lineof an example three-line power transmission line structure 4404, 4406,and 4408. When the ratio is near 1, point 4522, the UAS 4402 is centeredover the power transmission line structure, x=0 at point 4520.

A composite magnetic field (B-field) 4506 from all (3) wires shown inFIG. 45B. This field is an illustration of the strength of the magneticfield measured by one or more magnetic sensors in the UAS. In thisexample, the peak of the field 4508 corresponds to the UAS 4402 beingabove the location of the middle line 4406. When the UAS 4402 has twomagnetic sensors, the sensors would read strengths corresponding topoints 4502 and 4504. A computing system on the UAS or remote from theUAS, can calculate combined readings. Not all of the depicted componentsmay be required, however, and one or more implementations may includeadditional components not shown in the figure. Variations in thearrangement and type of the components may be made, and additionalcomponents, different components, or fewer components may be provided.

As an example of some implementations, a vehicle, such as a UAS, caninclude one or more navigation sensors, such as DNV sensors. Thevehicle's mission could be to travel to an initial destination andpossibly return to a final destination. Known navigation systems can beused to navigate the vehicle to an intermediate location. For example, aUAS can fly using GPS and/or human controlled navigation to theintermediate location. The UAS can then begin looking for the magneticsignature of a power source, such as power lines. To find a power line,the UAS can continually take measurements using the DNV sensors. The UAScan fly in a circle, straight line, curved pattern, etc. and monitor therecorded magnetic field. The magnetic field can be compared to knowncharacteristics of power lines to identify if a power line is in thevicinity of the UAS. For example, the measured magnetic field can becompared with known magnetic field characteristics of power lines toidentify the power line that is generating the measured magnetic field.In addition, information regarding the electrical infrastructure can beused in combination with the measured magnetic field to identify thecurrent source. For example, a database regarding magnetic measurementsfrom the area that were previously taken and recorded can be used tocompare the current readings to help determine the UAS's location.

In some implementations, once the UAS identifies a power line the UASpositions itself at a known elevation and position relative to the powerline. For example, as the UAS flies over a power line, the magneticfield will reach a maximum value and then begin to decrease as the UASmoves away from the power line. After one sweep of a known distance, theUAS can return to where the magnetic field was the strongest. Based uponknown characteristics of power lines and the magnetic readings, the UAScan determine the type of power line.

Once the current source has been identified, the UAS can change itselevation until the magnetic field is a known value that correspondswith an elevation above the identified power line. For example, as shownin FIG. 6, a magnetic field strength can be used to determine anelevation above the current source. The UAS can also use the measuredmagnetic field to position itself offset from directly above the powerline. For example, once the UAS is positioned above the current source,the UAS can move laterally to an offset position from the currentsource. For example, the UAS can move to be 10 kilometers to the left orright of the current source.

The UAS can be programmed, via a computer 306, with a flight path. Insome implementations, once the UAS establishes its position, the UAS canuse a flight path to reach its destination. In some implementations, themagnetic field generated by the transmission line is perpendicular tothe transmission line. In some implementations, the vehicle will flyperpendicular to the detected magnetic field. In one example, the UAScan follow the detected power line to its destination. In this example,the UAS will attempt to keep the detected magnetic field to be close tothe original magnetic field value. To do this, the UAS can changeelevation or move laterally to stay in its position relative to thepower line. For example, a power line that is rising in elevation wouldcause the detected magnetic field to increase in strength as thedistance between the UAS and power line decreased. The navigation systemof the UAS can detect this increased magnetic strength and increase theelevation of the UAS. In addition, on board instruments can provide anindication of the elevation of the UAS. The navigation system can alsomove the UAS laterally to the keep the UAS in the proper positionrelative to the power lines.

The magnetic field can become weaker or stronger, as the UAS drifts fromits position of the transmission line. As the change in the magneticfield is detected, the navigation system can make the appropriatecorrection. For a UAS that only has a single DNV sensor, when themagnetic field had decreased by more than a predetermined amount thenavigation system can make corrections. For example, the UAS can have anerror budget such that the UAS will attempt to correct its course if themeasured error is greater than the error budget. If the magnetic fieldhas decreased, the navigation system can instruct the UAS to move to theleft. The navigation system can continually monitor the magnetic fieldto see if moving to the left corrected the error. If the magnetic fieldfurther decreased, the navigation system can instruct the UAS to fly tothe right to its original position relative to the current source andthen move further to the right. If the magnetic field decreased instrength, the navigation system can deduce that the UAS needs todecrease its altitude to increase the magnetic field. In this example,the UAS would originally be flying directly over the current source, butthe distance between the current source and the UAS has increased due tothe current source being at a lower elevation. Using this feedback loopof the magnetic field, the navigation system can keep the UAS centeredor at an offset of the current source. The same analysis can be donewhen the magnetic field increases in strength. The navigation canmaneuver until the measured magnetic field is within the proper rangesuch that the UAS in within the flight path.

The UAS can also use the vector measurements from one or more DNVsensors to determine course corrections. The readings from the DNVsensor are vectors that indicate the direction of the sensed magneticfield. Once the UAS knows the location of the power line, as themagnitude of the sensed magnetic field decreases, the vector can providean indication of the direction the UAS should move to correct itscourse. For example, the strength of the magnetic field can be reducedby a threshold amount from its ideal location. The magnetic vector ofthis field can be used to indicate the direction the UAS should correctto increase the strength of the magnetic field. In other words, themagnetic field indicates the direction of the field and the UAS can usethis direction to determine the correct direction needed to increase thestrength of the magnetic field, which could correct the UAS flight pathto be back over the transmission wire.

Using multiple sensors on a single vehicle can reduce the amount ofmaneuvering that is needed or eliminate the maneuvering all together.Using the measured magnetic field from each of the multiple sensors, thenavigation system can determine if the UAS needs to correct its courseby moving left, right, up, or down. For example, if both DNV sensors arereading a stronger field, the navigation system can direct the UAS toincrease its altitude. As another example if the left sensor is strongerthan expected but the right sensor is weaker than expected, thenavigation system can move the UAS to the left.

In addition to the current readings from the one or more sensors, arecent history of readings can also be used by the navigation system toidentify how to correct the UAS course. For example, if the right sensorhad a brief increase in strength and then a decrease, while the leftsensor had a decrease, the navigation system can determine that the UAShas moved to far to the left of the flight path and could correct theposition of the UAS accordingly.

FIG. 46 illustrates a high-level block diagram of an example UASnavigation system 4600, according to some implementations of the subjecttechnology. In some implementations, the UAS navigation system of thesubject technology includes a number of DNV sensors 4602 a, 4602 b, and4602 c, a navigation database 4604, and a feedback loop that controlsthe UAS position and orientation. In other implementations, a vehiclecan contain a navigation control that is used to navigate the vehicle.For example, the navigation control can change the vehicle's direction,elevation, speed, etc. The DNV magnetic sensors 4602 a-4602 c have highsensitivity to magnetic fields, low C-SWAP and a fast settling time. TheDNV magnetic field measurements allow the UAS to align itself with thepower lines, via its characteristic magnetic field signature, and torapidly move along power-line routes. Not all of the depicted componentsmay be required, however, and one or more implementations may includeadditional components not shown in the figure. Variations in thearrangement and type of the components may be made, and additionalcomponents, different components, or fewer components may be provided.

FIG. 47 illustrates an example of a power line infrastructure. It isknown that widespread power line infrastructures, such as shown in FIG.47, connect cities, critical power system elements, homes andbusinesses. The infrastructure may include overhead and buried powerdistribution lines, transmission lines, railway catenary and 3rd railpower lines and underwater cables. Each element has a uniqueelectro-magnetic and spatial signature. It is understood that, unlikeelectric fields, the magnetic signature is minimally impacted byman-made structures and electrical shielding. It is understood thatspecific elements of the infrastructure will have distinct magnetic andspatial signatures and that discontinuities, cable droop, powerconsumption and other factors will create variations in magneticsignatures that can also be leveraged for navigation.

FIGS. 48A and 48B illustrate examples of magnetic field distribution foroverhead power lines and underground power cables. Both above-ground andburied power cables emit magnetic fields, which unlike electrical fieldsare not easily blocked or shielded. Natural Earth and other man-mademagnetic field sources can provide rough values of absolute location.However, the sensitive magnetic sensors described here can locate strongman-made magnetic sources, such as power lines, at substantialdistances. As the UAS moves, the measurements can be used to reveal thespatial structure of the magnetic source (point source, line source,etc.) and thus identify the power line as such. In addition, oncedetected the UAS can guide itself to the power line via its magneticstrength. Once the power line is located its structure is determined,and the power line route is followed and its characteristics arecompared to magnetic way points to determine absolute location. Fixedpower lines can provide precision location reference as the location andrelative position of poles and towers are known. A compact on-boarddatabase can provide reference signatures and location data forwaypoints. Not all of the depicted components may be required, however,and one or more implementations may include additional components notshown in the figure. Variations in the arrangement and type of thecomponents may be made, and additional components, different components,or fewer components may be provided.

FIG. 49 illustrates examples of magnetic field strength of power linesas a function of distance from the centerline showing that even lowcurrent distribution lines can be detected to distances in excess of 10km. Here it is understood that DNV sensors provide 0.01 uT sensitivity(Ie-10 T), and modeling results indicates that high current transmissionline (e.g. with 1000 A-4000 A) can be detected over many tens of km.These strong magnetic sources allow the UAS to guide itself to the powerlines where it can then align itself using localized relative fieldstrength and the characteristic patterns of the power-line configurationas described below.

FIG. 50 illustrates an example of a UAS 5002 equipped with DNV sensors5004 and 5006. FIG. 51 is a plot of a measured differential magneticfield sensed by the DNV sensors when in close proximity of the powerlines. While power line detection can be performed with only a singleDNV sensor precision alignment for complex wire configurations can beachieved using multiple arrayed sensors. For example, the differentialsignal can eliminate the influence of diurnal and seasonal variations infield strength. Not all of the depicted components may be required,however, and one or more implementations may include additionalcomponents not shown in the figure. Variations in the arrangement andtype of the components may be made, and additional components, differentcomponents, or fewer components may be provided.

In various other implementations, a vehicle can also be used to inspectpower transmission lines, power lines, and power utility equipment. Forexample, a vehicle can include one or more magnetic sensors, a magneticwaypoint database, and an interface to UAS flight control. The subjecttechnology may leverage high sensitivity to magnetic fields of DNVmagnetic sensors for magnetic field measurements. The DNV magneticsensor can also be low cost, space, weight, and power (C-SWAP) andbenefit from a fast settling time. The DNV magnetic field measurementsallow UASs to align themselves with the power lines, and to rapidly movealong power-line routes and navigate in poor visibility conditionsand/or in GPS-denied environments. It is understood that DNV-basedmagnetic sensors are approximately 100 times smaller than conventionalmagnetic sensors and have a reaction time that that is approximately100,000 times faster than sensors with similar sensitivity such as theEMDEX LLC Snap handheld magnetic field survey meter.

The fast settling time and low C-SWAP of the DNV sensor enables rapidmeasurement of detailed power line characteristics from low-C-SWAP UASsystems. In one or more implementations, power lines can be efficientlysurveyed via small unmanned aerial vehicles (UAVs) on a routine basisover long distance, which can identify emerging problems and issuesthrough automated field anomaly identification. In otherimplementations, a land based vehicle or submersible can be used toinspect power lines. Human inspectors are not required to perform theinitial inspections. The inspections of the subject technology arequantitative, and thus are not subject to human interpretation as remotevideo solutions may be.

FIG. 52 illustrates an example of a measured magnetic field distributionfor power lines 904 and power lines with anomalies 902 according to someimplementations. The peak value of the measured magnetic fielddistribution, for the normal power lines, is in the vicinity of thecenterline (e.g., d=0). The inspection method of the subject technologyis a high-speed anomaly mapping technique that can be employed forsingle and multi-wire transmission systems. The subject solution cantake advantage of existing software modeling tools for analyzing theinspection data. In one or more implementations, the data form a normalset of power lines may be used as a comparison reference for dataresulting from inspection of other power lines (e.g., with anomalies ordefects). Damage to wires and support structure alters the nominalmagnetic field characteristics and is detected by comparison withnominal magnetic field characteristics of the normal set of power lines.It is understood that the magnetic field measurement is minimallyimpacted by other structures such as buildings, trees, and the like.Accordingly, the measured magnetic field can be compared to the datafrom the normal set of power lines and the measured magnetic field'smagnitude and if different by a predetermined threshold the existence ofthe anomaly can be indicated. In addition, the vector reading betweenthe difference data can also be compared and used to determine theexistence of anomaly.

In some implementations, a vehicle may need to avoid objects that are intheir navigation path. For example, a ground vehicle may need tomaneuver around people or objects, or a flying vehicle may need to avoida building or power line equipment. In these implementations, thevehicle can be equipment with sensors that are used to locate theobstacles that are to be avoided. Systems such as a camera system, focalpoint array, radar, acoustic sensors, etc., can be used to identifyobstacles in the vehicles path. The navigation system can then identifya course correction to avoid the identified obstacles.

The herein described subject matter sometimes illustrates differentcomponents contained within, or connected with, different othercomponents. It is to be understood that such depicted architectures aremerely exemplary, and that in fact many other architectures can beimplemented which achieve the same functionality. In a conceptual sense,any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality can be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected,” or“operably coupled,” to each other to achieve the desired functionality,and any two components capable of being so associated can also be viewedas being “operably couplable,” to each other to achieve the desiredfunctionality. Specific examples of operably couplable include but arenot limited to physically mateable and/or physically interactingcomponents and/or wirelessly interactable and/or wirelessly interactingcomponents and/or logically interacting and/or logically interactablecomponents.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to inventions containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations). Furthermore, in those instances where a conventionanalogous to “at least one of A, B, and C, etc.” is used, in generalsuch a construction is intended in the sense one having skill in the artwould understand the convention (e.g., “a system having at least one ofA, B, and C” would include but not be limited to systems that have Aalone, B alone, C alone. A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). In those instances where aconvention analogous to “at least one of A, B, or C, etc.” is used, ingeneral such a construction is intended in the sense one having skill inthe art would understand the convention (e.g., “a system having at leastone of A, B, or C” would include but not be limited to systems that haveA alone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that virtually any disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be understood toinclude the possibilities of “A” or “B” or “A and B.” Further, unlessotherwise noted, the use of the words “approximate,” “about,” “around,”“substantially,” etc., mean plus or minus ten percent.

The foregoing description of illustrative embodiments has been presentedfor purposes of illustration and of description. It is not intended tobe exhaustive or limiting with respect to the precise form disclosed,and modifications and variations are possible in light of the aboveteachings or may be acquired from practice of the disclosed embodiments.It is intended that the scope of the invention be defined by the claimsappended hereto and their equivalents.

What is claimed is:
 1. A system for magnetic detection, comprising: amagneto-optical defect center sensor comprising: a magneto-opticaldefect center material comprising a plurality of magneto-optical defectcenters; a radio frequency (RF) excitation source configured to provideRF excitation to the magneto-optical defect center material; an opticalexcitation source configured to provide optical excitation to themagneto-optical defect center material; an optical detector configuredto receive an optical signal emitted by the magneto-optical defectcenter material, wherein the optical signal is based on hyperfine statesof the magneto-optical defect center material; a controller configuredto detect a gradient of the optical signal based on the hyperfine statesemitted by the magneto-optical defect center material; and a firstmagnetic field generator configured to generate a magnetic field,wherein the controller is further configured to: control the firstmagnetic field generator to apply a first time varying magnetic field atthe magneto-optical defect center material, determine a magnitude anddirection of the magnetic field at the magneto-optical defect centermaterial based on a received light detection signal from the opticaldetector; and determine a magnetic vector anomaly due to an object basedon the determined magnitude and direction of the magnetic fieldaccording to a frequency dependent attenuation of the time varyingmagnetic field.
 2. The system of claim 1, wherein the magneto-opticaldefect center sensor further comprises a reflector positioned about themagneto-optical defect center material to reflect a portion of lightemitted from the magneto-optical defect center material.
 3. The systemof claim 1, wherein the magneto-optical defect center sensor furthercomprises: a second magnetic field generator configured to generate asecond magnetic field; wherein the controller is further configured to:modulate a first code packet and control the first magnetic fieldgenerator to apply the first time varying magnetic field at themagneto-optical defect center material based on the modulated first codepacket, modulate a second code packet and control the second magneticfield generator to apply a second time varying magnetic field at themagneto-optical defect center based on the modulated second code packet,wherein the first code packet and the second code packet are binarysequences which have a low cross correlation with each other, and eachof the binary sequences has a good autocorrelation.
 4. The system ofclaim 3, wherein a direction of the first time varying magnetic field atthe magneto-optical defect center material is different from a directionof the second time varying magnetic field at the magneto-optical defectcenter material.
 5. The system of claim 3, wherein the controller isfurther configured to: receive first light detection signals from theoptical detector based on the optical signal emitted by themagneto-optical defect center material based on the first code packettransmitted to the magneto-optical defect center material, and receivesecond light detection signals from the optical detector based on theoptical signal emitted by the magneto-optical defect center materialbased on the second code packet transmitted to the magneto-opticaldefect center material simultaneous with the first code packet beingtransmitted to the magneto-optical defect center material; apply matchedfilters to the received first and second light detection signals todemodulate the first and second code packets; determine a magnitude anddirection of the first magnetic field and the second magnetic field atthe magneto-optical defect center material based on the demodulatedfirst and second code packets; and determine a magnetic vector anomalybased on the determined magnitude and direction of the first magneticfield and the second magnetic field.
 6. The system of claim 3, whereinthe first and second code packets are modulated by continuous phasemodulation.
 7. The system of claim 3, wherein the first and second codepackets are modulated by MSK frequency modulation.
 8. The system ofclaim 3, wherein the controller is further configured to control the RFexcitation source and the optical excitation source to provide asequence of pulses to the magneto-optical defect center material.
 9. Asystem for magnetic detection, comprising: a magneto-optical defectcenter sensor comprising: a magneto-optical defect center materialcomprising a plurality of magneto-optical defect centers; a radiofrequency (RF) excitation source configured to provide RF excitation tothe magneto-optical defect center material; an optical excitation sourceconfigured to provide optical excitation to the magneto-optical defectcenter material; an optical detector configured to receive an opticalsignal emitted by the magneto-optical defect center material, whereinthe optical signal is based on hyperfine states of the magneto-opticaldefect center material; a controller configured to detect a gradient ofthe optical signal based on the hyperfine states emitted by themagneto-optical defect center material; and a transmitting devicecomprising: a first processor configured to transmit data to atransmitter; and the transmitter, wherein the transmitter is configuredto transmit the data via a magnetic field.
 10. The system of claim 9,further comprising: a receiving device comprising: the magneto-opticaldefect center sensor configured to detect the magnetic field; and asecond processor configured to decipher the data from the detectedmagnetic field.
 11. The system of claim 10, wherein the first processoris further configured to: receive a first data stream comprising thedata; and interleave the data into a plurality of second data streams,and wherein the transmitter is configured to transmit each of the seconddata streams on one of a plurality of channels.
 12. The system of claim11, wherein each of the plurality of channels comprises one of aplurality of magnetic fields.
 13. The system of claim 12, wherein eachof the plurality of magnetic fields is orthogonal to one another. 14.The system of claim 11, wherein the magneto-optical defect center sensoris configured to detect the magnetic field in a plurality of directions.15. The system of claim 14, wherein the plurality of directions aretetrahedrally arranged.
 16. The system of claim 14, wherein the secondprocessor is configured to: receive a plurality of signals from themagneto-optical defect center sensor, wherein each of the plurality ofsignals corresponds to one of the plurality of directions; decipher eachof the plurality of second data streams from the plurality of signals;and de-interleave the plurality of second data streams to determine thedata.
 17. The system of claim 11, wherein to transmit the data via themagnetic field, the transmitter is configured to transmit two datastreams via two magnetic fields, and wherein each of the two datastreams corresponds to one of the two magnetic fields.
 18. The system ofclaim 11, wherein to transmit the data via a magnetic field, thetransmitter is configured to transmit three data streams via threemagnetic fields, wherein each of the three data streams corresponds toone of the three magnetic fields.
 19. The system of claim 11, whereinthe first processor is further configured to: receive a first datastream comprising the data; interleave the data into a plurality ofsecond data streams; and append a synchronization sequence to each ofthe plurality of second data streams to form a plurality of third datastreams, and wherein the transmitter is configured to transmit each ofthe third data streams on one of a plurality of channels.
 20. The systemof claim 19, wherein the magneto-optical defect center sensor isconfigured to detect the magnetic field in a plurality of directions,wherein the plurality of directions are orthogonal to one another; andwherein the second processor is configured to: receive a plurality ofsignals from the magneto-optical defect center sensor, wherein each ofthe plurality of signals corresponds to one of the plurality ofdirections; decipher each of the plurality of third data streams fromthe plurality of signals by detecting the sequence stream; andinterleave the plurality of third data streams to determine the data.21. A system for magnetic detection, comprising: a magneto-opticaldefect center sensor comprising: a magneto-optical defect centermaterial comprising a plurality of magneto-optical defect centers; aradio frequency (RF) excitation source configured to provide RFexcitation to the magneto-optical defect center material; an opticalexcitation source configured to provide optical excitation to themagneto-optical defect center material; an optical detector configuredto receive an optical signal emitted by the magneto-optical defectcenter material, wherein the optical signal is based on hyperfine statesof the magneto-optical defect center material; a controller configuredto detect a gradient of the optical signal based on the hyperfine statesemitted by the magneto-optical defect center material; a first magneticfield sensor that includes the magneto-optical defect center sensor, asecond magnetic field sensor that includes a second magneto-opticaldefect center sensor, and a position encoder component comprising amagnetic region configured to produce a magnetic field gradient from afirst end of the magnetic region to the second end of the magneticregion, wherein the first magnetic field sensor and the second magneticfield sensor are separated by a distance that is less than a length ofthe magnetic region.
 22. The system of claim 21, wherein the magneticregion comprises a ferromagnetic component having a cross-section at thefirst end of the magnetic region that is smaller than a cross-section atthe second end of the magnetic region.
 23. The system of claim 21,wherein the magnetic region comprises a magnetic polymer having amagnetic particle concentration at the first end of the magnetic regionthat is smaller than a magnetic particle concentration at the second endof the magnetic region.
 24. The system of claim 21, further comprising athird magnetic field sensor and a fourth magnetic field sensor.
 25. Thesystem of claim 21, wherein the position encoder component is a rotaryposition encoder.
 26. The system of claim 21, wherein the positionencoder component is a linear position encoder.
 27. The system of claim21, wherein the position encoder component further comprises a pluralityof the magnetic regions configured to produce a magnetic field gradientfrom a first end of the magnetic region to the second end of themagnetic region arranged end to end on the position encoder component.28. The system of claim 1, further comprising an acoustic transmitterconfigured to transmit an acoustic signal through a fluid with dissolvedions, wherein the magneto-optical defect center sensor is configured todetect the acoustic signal through the fluid.
 29. The system of claim 1,further comprising: a vehicle that includes the magneto-optical defectcenter sensor, wherein the magneto-optical defect center sensor isconfigured to detect a magnetic vector or a magnetic field; one or moreelectronic processors configured to: receive the magnetic vector of themagnetic field from the magneto-optical defect center sensor; anddetermine a presence of a current source based upon the magnetic vector;and a navigation control configured to navigate the vehicle based uponthe presence of the current source and the magnetic vector.
 30. Thesystem of claim 1, wherein the magneto-optical defect center materialcomprises a nitrogen vacancy (NV) diamond material comprising aplurality of NV centers.
 31. The system of claim 9, wherein themagneto-optical defect center material comprises a nitrogen vacancy (NV)diamond material comprising a plurality of NV centers.
 32. The system ofclaim 21, wherein the magneto-optical defect center material comprises anitrogen vacancy (NV) diamond material comprising a plurality of NVcenters.